The Cambridge Computer Lab Ring
£184.7bn aggregate value as of 2026-01-19
372 companies in the Hall of Fame
150 active 72 acquired 145 inactive
A note on the number. ARM Holdings accounts for around £166 billion of this total — approximately 90% of the headline figure. The remaining 371 companies represent a documented £18.3bn between them. Stephen Allott's argument has never been about captured value; it is about network amplification at the level of the cluster. The ARM concentration is a feature of the data to face honestly, not to elide. Read the thesis.
Foundings per decade
Top ten by valuation
ARM's scale is visible. The axis is honest.
All 372 companies
Only 75 of 372 companies have a published valuation; the headline figure is a floor, not an estimate of the full total.
Status:
| Company | Founder(s) | Founded | Status | Location | Valuation | Employees |
|---|---|---|---|---|---|---|
| Acorn Computer | Andy Hopper | 1979 | Inactive | — | — | — |
| Active Media Solutions | John Bates, Giles Nelson | 1995 | Inactive | North West | — | — |
| Actuarial Solutions Ltd | Martin Barringer | 1999 | Active | South East | — | 1 |
| Acunu | Tim Moreton, Tom Wilkie, Andy Twigg | 2009 | Inactive | London | £9m | — |
| Adaptive Broadband | Andy Hopper | 1997 | Acquired | London | £9m | — |
| Adventiq | Andy Hopper | 2005 | Active | East of England | — | 5 |
| Aesthetic Integration | Grant Olney Passmore | 2014 | Active | London | — | 25 |
| Aircloak | Sebastian Probst Eide | 2014 | Inactive | — | — | — |
| Aluma | George Harpur | 2009 | Active | East of England | £10m | — |
| Amino Communications | Paul Fellows | 1998 | Active | East of England | — | 17 |
| Angani | Ripduman Sohan | 2013 | Active | — | — | — |
| Angel Alerts Ltd | Dinan Gunawardena | 2012 | Inactive | East of England | — | — |
| Anidium | Igor Drokov | 2015 | Active | East of England | — | 2 |
| Anondesign | Conchur Dickinson, Simon Freytag | 1999 | Active | — | — | — |
| AnswerGrid | Noah Ohrner | 2024 | Active | — | — | — |
| ANT | Nicko van Someren FREng | 1992 | Inactive | — | — | — |
| Anvil | Ian Davies, Meredydd Luff | 2015 | Active | East of England | — | 9 |
| Apama | John Bates, Giles Nelson | 1999 | Acquired | South East | — | — |
| APM Ltd | Andrew Herbert | 1985 | Acquired | — | — | — |
| AppChocolate | Oliver Lamming | 2014 | Active | East of England | — | 2 |
| Applied Generics | Joe Dixon, Bruce Adam, Ian Atkinson | 1999 | Acquired | East of Scotland | — | 18 |
| AQrex | Conchur Dickinson | 2007 | Inactive | London | — | — |
| ARM | Mike Muller | 1990 | Active | East of England | £166.3bn | 3,346 |
| Advanced Rendering Technology | Daniel Hall, Adrian Wrigley | 1995 | Inactive | — | — | — |
| Artimi | Jack Lang | 2002 | Acquired | London | — | — |
| Arva AI | Oliver Wales | 2024 | Active | London | — | — |
| Axiomatic Technology Ltd | David Moore | 1994 | Active | East Midlands | — | 8 |
| Axxeltrova | Faisal Ahmed | 2009 | Active | London | — | 3 |
| Azuro | Paul Cunningham, Steeve Wilcox | 2002 | Acquired | — | — | — |
| Bango | Ray Anderson | 1999 | Active | East of England | — | 113 |
| Bantr | Toby Austin | 2010 | Inactive | East of England | £1m | — |
| Basis Communications | Gavin Stark | 1998 | Acquired | — | £370m | — |
| Beauhurst | Toby Austin | 2010 | Active | London | £40m | 128 |
| BERI Open Systems CIC | Ben Laurie, Simon Moore, Robert Watson | 2013 | Unknown | — | — | — |
| Bid Management Ltd | Paul Beard | 2002 | Inactive | London | — | — |
| Biodot Ltd | P Shaw | 1987 | Active | South East | — | 10 |
| BitX (Luno) | Nicholas Pilkington | 2013 | Acquired | — | — | 400 |
| blinkx | Suranga Chandratillake | 2004 | Inactive | London | — | 9 |
| Blue Compass | Chris Timms | 2003 | Inactive | — | — | — |
| Boldport | Saar Drimer | 2010 | Inactive | London | — | 2 |
| Blue technologies | Tom Godber, Sean Mullaney | 2001 | Inactive | London | — | — |
| break-step productions | Kona Macphee | 2001 | Inactive | London | — | — |
| Bromium | Simon Crosby, Ian Pratt | 2010 | Acquired | East of England | £197m | — |
| Browser to Buyer | Dave Gowans | 2016 | Active | London | — | 3 |
| Business Web Software | Grant Husbands, Giles Mitton | 2001 | Inactive | — | — | — |
| Bytemark | Matthew Bloch, Peter Taphouse | 2002 | Acquired | London | £2m | — |
| CacheLogic | Adam Twiss | 2002 | Acquired | — | — | — |
| Calipsa | Rashid Khan | 2016 | Active | London | £8m | — |
| Cambridge Broadband | Andy Hopper | 2000 | Active | East of England | £98m | 25 |
| Cambridge Coding Academy | Andrius Aucinas, Raoul-Gabriel Urma | 2014 | Inactive | East of England | — | 1 |
| Cambridge Cyber Limited | Frank Stajano, Graham Rymer | 2016 | Active | East of England | — | — |
| Cambridge Ring | Stephen Allott, Ian Leslie | 2002 | Active | — | — | 1 |
| Cambridge Spark | Raoul-Gabriel Urma | 2016 | Active | East of England | — | 141 |
| Cambridge Visual Networks | Quentin Stafford-Fraser | 2007 | Inactive | London | — | — |
| Camdata Ltd | Peter Cowley | 1984 | Active | East of England | — | 2 |
| Camrivox | Jonathan Custance, James Green | 2005 | Inactive | East of England | — | 8 |
| Cantab Wireless | Juha Korhonen | 2007 | Inactive | East of England | — | — |
| Capabilities Limited | Ben Laurie, Robert Watson | 2011 | Active | Wales | — | 11 |
| Carrington Computer Consultants Ltd | Tim Coote, Graham Pattie | 1982 | Inactive | — | — | — |
| CatchApp | Oliver Lamming | 2015 | Active | London | £6m | 6 |
| Cedalion | Chris Galley | 1995 | Acquired | London | — | — |
| Censeo Systems | Peter Jones | 2003 | Inactive | South West | — | — |
| Charisma.ai | Ben Salili-James | 2015 | Active | South East | £3m | 7 |
| Climate Code Foundation | Nick Barnes | 2010 | Inactive | Yorkshire and The Humber | — | — |
| Clusterfudge | George Thomas | 2023 | Active | London | £6m | 4 |
| CodeThink | Robert Taylor | 2007 | Active | North West | £1m | 109 |
| Codian | David Holloway, Will MacDonald | 2003 | Acquired | — | £220m | — |
| CoFarm Foundation | Laura James | 2018 | Active | East of England | — | — |
| Cognitive Solutions AG | Stefan G Hild | 2016 | Acquired | — | — | — |
| Collabora | Robert McQueen, Robert Taylor | 2005 | Active | East of England | — | 54 |
| Contengo | Charles Southey | 2020 | Unknown | — | — | — |
| Corral | Noam Szpiro | 2012 | Inactive | — | — | — |
| Cotares | Alan Jones | 2002 | Inactive | East of England | — | 2 |
| CPlane | Ian Leslie, Simon Crosby | 1999 | Inactive | — | — | — |
| Creature House | Alex Hsu Siu Chi | 1994 | Acquired | East of England | — | — |
| Cronto | Igor Drokov | 2005 | Acquired | — | — | — |
| Cube AI | Louis de Benoist | 2023 | Active | — | — | — |
| Cunning Running Software | Christopher Barrington Brown | 1988 | Active | South East | — | 10 |
| Curious Software | Justin Wise | 1999 | Inactive | London | — | — |
| DataCore Software | Nick Connolly | 1998 | Active | — | — | 350 |
| Datoral.com | David Mack | 2013 | Inactive | — | — | — |
| Datanomic | Richard Marsh | 2001 | Acquired | South East | — | — |
| DeepMind Technologies | Demis Hassabis | 2010 | Acquired | London | £327m | 2,600 |
| Detective Hero | Jonathan Goddard | 2020 | Inactive | — | — | — |
| Devyce Inc. | Edward Clayton | 2020 | Active | (no value) | — | — |
| Digital Mail | Robert Darwin | 1991 | Active | London | — | — |
| Digitivity | Andrew Herbert | 1996 | Acquired | London | — | — |
| Disguise | Ashraf Nehru | 2003 | Unknown | — | — | — |
| DisplayLink | Quentin Stafford-Fraser | 2003 | Acquired | — | £248m | — |
| dividiti | Anton Lokhmotov | 2014 | Inactive | East of England | — | 2 |
| DroneDeploy | Nicholas Pilkington | 2013 | Active | — | — | 350 |
| D2 Legal Technology | Akber Datoo | 2011 | Active | London | — | 19 |
| DuffGun Ltd | Dinan Gunawardena | 2012 | Inactive | East of England | — | — |
| eCosCentric | Nick Garnett, Jonathan Larmour | 2002 | Active | East of England | — | 5 |
| Egis.ly | Craig Dean | 2019 | Active | North West | — | — |
| Electric Software | Jeff Fenton | 2009 | Inactive | London | — | — |
| Electronic Share Information | Jack Lang | 1993 | Acquired | London | — | — |
| Element | Matthew Hodgson | 2017 | Active | London | £124m | 103 |
| Elixir Studios | Demis Hassabis | 1998 | Inactive | South West | — | — |
| Ellexus | Rosemary Francis | 2010 | Inactive | West Midlands | — | 6 |
| Eluceda | Peter Cowley | 2009 | Active | North West | £3m | 12 |
| Embecosm | Jeremy Bennett | 2008 | Active | South East | — | 10 |
| Embue | Robert Cooper | 2015 | Inactive | Wales | — | 1 |
| emotif.ai | Rory Waite | 2019 | Inactive | London | — | 4 |
| Emotiful Inc | Dinan Gunawardena | 2013 | Inactive | — | — | — |
| Encoded Media | Tom Sillence | 2003 | Inactive | London | — | — |
| Encore | James King, James McAulay | 2014 | Inactive | East of England | £8m | 21 |
| English Language iTutoring | Ted Briscoe | 2014 | Acquired | — | — | — |
| Envisional | Ben Coppin | 1999 | Inactive | East of England | — | — |
| ePlantData Inc | Rurik Turton | — | Inactive | — | — | — |
| EPT Computing | Martin Kleppmann | 2007 | Acquired | East of England | — | — |
| Equisys | Chris Oswald, Gareth Williams | 1987 | Active | London | — | 23 |
| Eshinui Inc | Carl Dellar | 2000 | Inactive | — | — | — |
| Ethicronics | Franck Courbon | 2022 | Active | East of England | — | 3 |
| Evertrack | Dominic Edmonds | 1994 | Inactive | East of England | — | — |
| Evi | William Tunstall-Pedoe | 2005 | Acquired | London | £21m | 624 |
| EXAPSYS | Yannis Papaefstathiou | 2019 | Active | — | — | — |
| Exbiblio | Quentin Stafford-Fraser | 2004 | Acquired | — | — | — |
| Factmata | Andreas Vlachos | 2016 | Active | London | — | — |
| Felicite.com Inc | Hans Hsu | 1999 | Acquired | — | — | — |
| FeedHenry | Mícheál Ó Foghlú | 2008 | Acquired | — | £53m | — |
| Fendragon Ltd | John Harradine, Mick Jordan, David Kindersley, Peter Robinson, Neil Wiseman | 1977 | Inactive | East of England | — | — |
| Fen Research | Andrew Gower | 2010 | Active | East of England | — | 8 |
| Filonet Korea Incorporated | Jong-Hyeon Lee | 2000 | Inactive | — | — | — |
| Fidgety Lizard Limited | Kona Macphee | 2015 | Active | West of Scotland | — | 2 |
| Finfo Ltd | Stu McLellan | 2018 | Inactive | Yorkshire and The Humber | — | — |
| First DBS Ltd | Andy Rawson | 1985 | Inactive | South East | — | — |
| F-LEX Legal Ltd | James Moore | 2016 | Active | London | £1m | 96 |
| Flower Labs | Daniel Beutel, Taner Topal, Nicholas Lane | 2020 | Active | London | — | 7 |
| Fluent | Alan Mitchell | 2007 | Active | London | £26m | 10 |
| Focal Point Positioning | Ramsey Faragher | 2015 | Active | East of England | £76m | 50 |
| FORE Systems | Robert Sansom | 1990 | Acquired | South West | £3.6bn | — |
| FountainArc | Chi Lee | 2018 | Active | South East | — | 1 |
| Fraser Research | Sandy Fraser | 2002 | Inactive | — | — | — |
| FusePump | Robert Durkin, Chris Conn | 2009 | Inactive | London | £0m | 22 |
| Generative Engineering | Nick Boultbee | 2023 | Active | West Midlands | £32m | 12 |
| Genius 2000 | William Tunstall-Pedoe | 1998 | Active | East of England | — | 1 |
| GeoSpock | Steven Marsh | 2013 | Inactive | East of England | £38m | 2 |
| Global Inkjet Systems | Nick Geddes | 2006 | Active | East of England | — | 68 |
| Global Software Publishing | Jeff Fenton | 1985 | Acquired | — | — | — |
| Globosense | Marcelo Pias | 2009 | Inactive | East of England | — | — |
| Governor Technology Ltd | John Mannix | 2001 | Acquired | — | — | — |
| GradChef | Ming Yin | 2013 | Acquired | — | — | — |
| GradFutures | Toby Austin | 2007 | Inactive | South East | — | — |
| Grapeshot | Martin Porter | 2002 | Acquired | South East | £150m | — |
| Great East London Software | Philip Moore | 2002 | Active | East of England | — | 2 |
| Green Custard | Jonathan Custance, James Green | 2009 | Active | East of England | — | 17 |
| Grex Games | Adam Martin | 2001 | Inactive | South East | — | — |
| Groopit.com | Tom Griffiths | 2006 | Inactive | Wales | — | — |
| GST Technolgies | Jeff Fenton | 1979 | Inactive | — | — | — |
| HandsetExpert | Shahrum Nedjati-Gilani | 2014 | Active | London | — | 1 |
| Health2Works | Roger Marlow | 2010 | Active | West Midlands | £1m | 3 |
| Hindsight Software Ltd | Jack Bastow | 2012 | Active | South East | — | 3 |
| Hitch | Noam Szpiro | 2014 | Acquired | — | — | — |
| Hubbub | Jonathan May | 2011 | Active | London | £3m | 13 |
| Hubdub | Tom Griffiths | 2007 | Inactive | — | — | — |
| Hyran Technologies | Ahmed Zaidi, Jordan Zhang | 2022 | Active | East of England | — | 1 |
| IdeaWorks3D | Eben Upton | 1998 | Inactive | — | — | — |
| iKVA | Richard Mortier, Liang Wang, Jon Crowcroft | 2017 | Active | East of England | £3m | — |
| iLexIR | Ted Briscoe | 2003 | Active | East of England | — | — |
| Imense Ltd | Chris Town | 2007 | Active | East of England | — | 2 |
| Improbable.io | Herman Narula, Robert Whitehead | 2012 | Active | London | £2.8bn | 212 |
| Indigo Panda Labs Inc | Yarden Eitan, Matthew Lent | 2014 | Inactive | — | — | — |
| Infact Ltd | Mark Jones | 1985 | Acquired | — | — | — |
| Innonation Productions | Justin Siu | 2004 | Inactive | — | — | — |
| Innovation Framework Technologies | Colin Palombo | 2006 | Inactive | — | — | — |
| Insight Studios | Tom Griffiths | 2004 | Inactive | Wales | — | — |
| In-Silica | Richard Watts | 2007 | Active | East of England | — | 10 |
| Invention Marketing | Nicky Dibben | 1999 | Inactive | East of England | — | — |
| Invest Solutions | John Fawcett, Matthew Parkinson, Andrew Rice | 2002 | Inactive | North West | — | 1 |
| Ionsquare | Oleg Podsechin | 2001 | Inactive | East of England | — | — |
| Ionysys Technology Corporation | Richard Mason | 1996 | Acquired | — | — | — |
| IPV Limited | Andy Hopper | 1996 | Active | East of England | £9m | 47 |
| Iridian Technologies | John Daugman | 1990 | Active | — | — | — |
| Jagex | Andrew Gower | 2001 | Active | East of England | £910m | 495 |
| Jakyl | Jeremy Adams | 2009 | Active | South West | — | 2 |
| Janus Technology | Matthew Faupel | 2010 | Active | East of England | — | 12 |
| Jawa Soft | Ewan Makepeace | 2001 | Active | — | — | — |
| JMEC | John Moore | 1989 | Inactive | — | — | — |
| Jobstream Group | John Brimacombe | 1993 | Inactive | London | — | 24 |
| JourneyLog | Alasdair Scott | 2009 | Active | South East | — | 2 |
| Kavanagh | Rob Campbell | 1996 | Inactive | — | — | — |
| KBW Consulting | Nat Billington, Lorenzo Wood | 1992 | Acquired | North West | — | 2 |
| KeyChest Ltd | Dan Cvrcek | 2019 | Inactive | East of England | — | — |
| Kinhub | Helen Yannakoudakis | 2019 | Active | London | £10m | 2 |
| KnowledgeSpaces | Jochen L Leidner | 2022 | Inactive | — | — | — |
| Koder.ly | Craig Dean | 2000 | Active | North West | — | 16 |
| KRAI | Anton Lokhmotov | 2020 | Active | East of England | — | 10 |
| Kular | Saaras Mehan | 2021 | Active | — | — | — |
| Leading Technology Inc | Peter Jones | 1989 | Inactive | — | — | — |
| Lemur Consulting | Richard Boulton | 2001 | Inactive | South West | — | 1 |
| Level 5 Networks | Andy Hopper, Steve Pope | 2002 | Acquired | — | — | — |
| Linguamatics | Roger Hale, David Milward, James Thomas, Sylvia Knight | 2001 | Acquired | South East | — | — |
| Linguit GmbH | Jochen Leidner | 2001 | Inactive | — | — | — |
| Listing Monster AI | James Moore | 2023 | Active | — | — | — |
| LogicIQ | Jan Hruska | 2006 | Inactive | South East | — | — |
| Lone Rooftop | Reinoud Elhorst | 2015 | Acquired | — | — | — |
| lowRISC | Rob Mullins, Alex Bradbury, Gavin Ferris | 2014 | Active | East of England | — | 22 |
| Lumeter | Mitra Ardron | 2012 | Active | West Midlands | — | 5 |
| MagicSolver | Oliver Lamming, Leon Palm | 2009 | Inactive | East of England | — | — |
| Mango Health | Gerald Cheong | 2012 | Inactive | — | — | — |
| Masabi | Tom Godber, Sean Mullaney | 2001 | Active | London | £68m | 183 |
| Media Dynamics | Gerald Ratzer | 1968 | Inactive | London | — | — |
| MessageLabs | Alex Shipp | 1999 | Acquired | London | — | — |
| Metanate | John Stark | 2000 | Inactive | East of England | — | 3 |
| Metrica Systems | Peter Jones | 1993 | Acquired | — | — | — |
| Micro Focus | Stewart Lang | 1976 | Active | South East | £1.8bn | 11,000 |
| Micropraxis Ltd | Matthew Faupel | 2001 | Active | East of England | — | — |
| Midsummer House | Jack Lang | 1998 | Active | East of England | — | — |
| Mitcham Technologies | Richard Mason | 1996 | Inactive | East of England | — | — |
| MJDK Consulting Ltd | Mateusz Jadczak | 2016 | Inactive | London | — | — |
| Go Mobile | Juanito Camilleri | 1999 | Active | — | — | — |
| Moon Express | Barney Pell | 2010 | Inactive | South East | — | — |
| Monigo | Declan Conlon | 2020 | Active | — | — | — |
| Muscat Ltd | Martin Porter | 1995 | Acquired | London | — | — |
| MyMoneyDog | Nicholas Pilkington | 2010 | Inactive | East of England | — | — |
| NetFPGA | Andrew Moore, Robert Watson | 2015 | Active | East of England | — | 3 |
| nCipher | Nicko van Someren | 1999 | Acquired | East of England | £51m | — |
| Ndiyo! | Quentin Stafford-Fraser | 2002 | Inactive | East of England | — | — |
| Nemesys Research | Ian Leslie, Derek McAuley, Joe Dixon, Cosmos Nicolaou, Ian Pratt | 1994 | Acquired | — | — | — |
| NetChannel Ltd | Jack Lang | 1995 | Acquired | London | — | — |
| Netronome | Niel Viljoen | 2003 | Active | — | — | — |
| NextBase Ltd | Mark Atheron, Ian Mercer | 1988 | Acquired | London | — | 136 |
| nGame | John Brimacombe | 1997 | Inactive | East of England | — | — |
| Nine Tiles | John Grant | 1978 | Inactive | East of England | — | — |
| Northpoint Services Ltd | Matt Kingswood | 2004 | Acquired | East of England | — | — |
| Objectronix | Chris Royle | 1997 | Inactive | Yorkshire and The Humber | — | — |
| ObjectSecurity | Ulrich Lang | 1999 | Inactive | East of England | — | 2 |
| Ocelot Consulting | David Wolfram | 2014 | Inactive | London | — | — |
| Olivetti Research Laboratory | Andy Hopper | 1986 | Acquired | — | — | — |
| Omnipotent Software | Charles Southey | 2004 | Inactive | — | — | — |
| Operis Plc | David Colver | 1997 | Active | London | — | 71 |
| OptionExist | Stephen Love | 1993 | Inactive | — | — | — |
| Orbis | Andy Hopper | 1978 | Acquired | — | — | — |
| Packet Ship | Paul Clark | 2005 | Inactive | South West | — | — |
| Paradigm Design Systems | Paul Cunningham, Steev Wilcox | 2001 | Inactive | — | — | — |
| Patientline | Philip Rushby | 1994 | Acquired | South East | — | 1,320 |
| PC Communications Ltd | Philip Rushby | 1985 | Inactive | Yorkshire and The Humber | — | — |
| PCF Ltd | Richard Jebb | 1982 | Acquired | — | — | — |
| Perfect Image | Andrew Robson | 1991 | Active | North East | — | 124 |
| Perihelion Software Ltd | Tim King | 1986 | Acquired | — | — | — |
| PetaGene | Dan Greenfield | 2016 | Active | East of England | £9m | 10 |
| Pirical | Hok-Him Poon | 2015 | Active | London | — | 41 |
| Planetary Processing Ltd | Samuel Sully | 2022 | Inactive | South West | £3m | 3 |
| PolyAI | Nikola Mrksic | 2017 | Active | London | £403m | 159 |
| Powerset | Barney Pell | 2006 | Acquired | East Midlands | — | — |
| Projected Games | Philip Hewinson | 2005 | Active | Wales | — | 1 |
| PSDT | Peter Scott | 1999 | Inactive | South East | — | — |
| Qudos | Andy Hopper | 1985 | Inactive | South West | — | — |
| Questionmark | John Kleeman | 1988 | Active | North West | £19m | 31 |
| Rapportive | Martin Kleppmann, Sam Stokes, Rahul Vohra | 2010 | Acquired | — | — | — |
| Raspberry Pi | Jack Lang, Robert Mullins, Alan Mycroft, Eben Upton | 2009 | Active | East of England | £1.1bn | 129 |
| RealVNC | Andy Harter, Andy Hopper, Tristan Richardson, James Weatherall | 2002 | Active | East of England | — | — |
| Reconfigure.io | Robert Taylor | 2015 | Inactive | East of England | £3m | — |
| Redbeacon | Aaron Lee | 2008 | Acquired | — | — | — |
| Red Glasses | Adam Martin | 2009 | Inactive | London | — | — |
| re:infer | Marius Cobzarenco | 2015 | Inactive | London | £21m | 24 |
| RoboK | Chao Gao, Liangchuan Gu | 2017 | Active | East of England | £7m | 7 |
| Robotae | Kevin Rathbone | 2014 | Active | East of England | — | 1 |
| Rormix | Mark Wheeler | 2013 | Inactive | North West | £1m | — |
| Rubicon Software | Alistair Hancock | 1989 | Active | South East | — | 10 |
| Sano Genetics (previously Heterogeneous) | Will Jones | 2017 | Active | London | £48m | 66 |
| Saviso Group | Adam Twiss | 1995 | Inactive | — | — | — |
| Saxonica | Michael Kay | 2004 | Active | South East | — | 6 |
| Seventh String | Andy Robinson | 2003 | Active | London | — | 1 |
| Shadow Robot Company | Rich Walker | 1997 | Active | London | — | 20 |
| Shape Data Ltd | Ian Braid, Alan Grayer, Charles Lang, Peter Veenman | 1974 | Acquired | East Midlands | — | 1 |
| Shopfitter | Chris Galley | 1999 | Active | North East | — | 2 |
| Simulacra | Patrick Towell | 1997 | Inactive | — | — | — |
| Sintefex Audio | Mike Kemp | 1997 | Inactive | (no value) | — | — |
| Sketch-Deck | David Mack | 2013 | Inactive | East of England | — | — |
| Skygate Technology | Pete Chown | 1996 | Inactive | London | — | — |
| Smart Crib | Dan Cvrcek | 2011 | Inactive | East of England | — | — |
| SmarterQueue | Claude Schneider | 2016 | Active | London | — | 1 |
| SmartInfoSearch | Chris Charlton, Calum Grant | 2003 | Inactive | East of England | — | — |
| Sociality | Ian Benson | 1999 | Inactive | — | — | — |
| SoftForum | Jong-Hyeon Lee | 1995 | Active | — | — | — |
| Software Integrators | Nick Barratt | 1988 | Active | London | — | 26 |
| Software Solutions | Paul Fellows | 1989 | Inactive | — | — | — |
| Sonic Pi | Sam Aaron | 2018 | Unknown | — | — | — |
| Sophos | Jan Hruska | 1985 | Active | London | £3.2bn | 4,400 |
| Spaceward Microsystems Ltd | Mike Kemp | 1983 | Inactive | — | — | — |
| Spaceward Studios | Mike Kemp | 1972 | Inactive | — | — | — |
| Spark! Data | Lee Fedder | 1996 | Inactive | East of England | — | — |
| Speechmatics | Tony Robinson | 2006 | Active | East of England | £131m | 117 |
| Spektrix | Michael Nabarro | 2008 | Active | London | £1m | 248 |
| SRI Cambridge | Ian Benson | 1985 | Inactive | — | — | — |
| Starfish Development Ltd | Peter Cowley | 2000 | Inactive | South East | — | 1 |
| STARFISH | Richard Mason | 2005 | Inactive | — | — | — |
| StartHQ | Oleg Podsechin | 2011 | Active | London | — | 1 |
| StegoStik | Glen Slade | 2004 | Inactive | London | — | — |
| Studio Audio and Video Ltd | Mike Kemp | 1991 | Inactive | East of England | — | — |
| Superhuman | Rahul Vohra | 2015 | Active | — | £673m | 150 |
| Survey Online | Chris Galley | 1999 | Acquired | — | — | — |
| SwiftKey (TouchType Ltd) | Ben Medlock | 2008 | Acquired | London | £205m | — |
| Sygneca | Jon Pretty | 2004 | Inactive | South East | — | — |
| Synergy Energy | Nat Billington | 2011 | Inactive | — | — | — |
| Synthesized.io | Alexander Kuhnle | 2018 | Active | London | £41m | 14 |
| Tarragon Embedded Technology | John Botham, Steve Montgomery | 1996 | Acquired | — | — | — |
| TechWolf | Jeroen Van Hautte | 2018 | Active | London | — | 10 |
| Telemarq | Quentin Stafford-Fraser | 2011 | Active | East of England | — | — |
| Tenison Technology EDA | David Greaves | 2000 | Acquired | — | — | — |
| Tenyks | Botty Dimanov, Dmitry Kazhdan, Maleakhi Wijaya | 2019 | Active | East of England | — | 8 |
| ThatsMyFace | Mark Cardle | 2008 | Active | — | — | — |
| Three-Space Ltd | Charles Lang | 1986 | Inactive | — | — | — |
| Tideway Systems | Tim Coote, Duncan Grisby | 2002 | Acquired | South East | — | — |
| Tractable | Razvan Ranca | 2014 | Active | London | £0m | 191 |
| Trampoline Systems | Craig McMillan | 2003 | Inactive | London | — | — |
| Transentia | Toby Austin | 2008 | Inactive | East of England | — | — |
| Transport Telematics | Neil Barton | 2008 | Inactive | South East | — | 3 |
| Trigger.io | James Brady | 2008 | Inactive | — | — | — |
| Trinamo | Stephen Allott | 2005 | Inactive | London | — | — |
| Turing Talent | Christina Xi Chen | 2018 | Active | Wales | — | 4 |
| Twigkit | Bjarki Holm | 2009 | Acquired | — | — | — |
| TxTEz | Andy Hopper, Ripduman Sohan | 2013 | Inactive | East of England | — | — |
| TypeDB | Haikal Pribadi | 2015 | Active | East of England | £11m | 11 |
| Typeset | Bjarki Holm | 2020 | Acquired | — | — | — |
| 1248 | Pilgrim Beart | 2013 | Inactive | — | — | — |
| Ubisense | Andy Hopper | 2002 | Active | East of England | — | 81 |
| UK Broadband Ltd | Faisal Ahmed | 2001 | Acquired | — | — | — |
| Unikernel Systems | Amir Chaudhry, Thomas Gazagnaire, Thomas Leonard, Anil Madhavapeddy, Mindy Preston, David Sheets, Balraj Singh, Magnus Skjegstad, Jeremy Yallop | 2015 | Acquired | East of England | — | — |
| UK Online | Tim King | 1994 | Acquired | — | — | — |
| UsefulBird | Indigo Orton | 2022 | Inactive | — | — | — |
| Versed AI | Simon Baker | 2019 | Active | London | £5m | 11 |
| VeriQual | Samir-Ali Feroze | 2004 | Inactive | South East | — | — |
| Vipadia | Neil Stratford | 2005 | Acquired | East of England | — | — |
| Virata Ltd | David Greaves, Andy Hopper | 1993 | Acquired | — | — | — |
| Viriturr | Robert Edwin Rouse | 2023 | Unknown | — | — | — |
| Volemic | Primoz Fabiani | 2021 | Active | East of England | — | 1 |
| VyperCore | Russell Haggar | 2022 | Inactive | East of England | £8m | 1 |
| Wizix | Philip Rushby | 2014 | Inactive | London | — | — |
| Xandera | Richard Mason | 2000 | Acquired | — | — | — |
| Xapien | Daniel Secretan | 2018 | Active | East of England | £28m | 45 |
| XenSource | Simon Crosby, Keir Fraser, Steven Hand, Ian Pratt | 2005 | Acquired | London | £410m | — |
| Xi Software Ltd | John Collins | 1986 | Active | London | — | 1 |
| Xitu Inc | Ming Yin | 2015 | Active | — | — | — |
| Xsilon | Russell Haggar | 2008 | Inactive | South East | £1m | — |
| Xynchron Ltd | Rurik Turton | 2002 | Inactive | London | — | — |
| YossarianLives! | Ekaterina Shutova | 2011 | Inactive | — | — | — |
| Yudkin Consulting AG | Mark Yudkin | 1989 | Inactive | — | — | — |
| Zeus Technology | Damian Reeves, Adam Twiss | 1995 | Acquired | London | £90m | — |
| Zoonami | Martin Hollis | 2000 | Inactive | East of England | — | — |
| Stealth | Alexander Kuhnle | — | Active | — | — | — |
| Involve Education (Practice Pal) | James King | 2023 | Active | London | £11m | 10 |
| Wedissmo | Oliver Lamming | 2024 | Active | London | £5m | 2 |
| ChipFlow | Rob Taylor | 2021 | Active | East of England | £6m | 6 |
| Silicon Futures | Jonathan May | 2009 | Inactive | South East | — | — |
| Annexable Microelectronics | Jonathan May | 2010 | Inactive | South West | — | — |
| TangibleFX | Jonathan May | 2011 | Inactive | South West | — | — |
| DeepMap | Mark Wheeler | 2016 | Acquired | — | £350m | — |
| Vox Live | Robert Dirkin | 2023 | Active | Yorkshire and The Humber | — | 2 |
| Toughbyte | Oleg Podsechin | 2015 | Active | — | — | 34 |
| Hone | Tom Griffiths | 2018 | Active | — | — | 152 |
| Starleaf | Will MacDonald | 2008 | Inactive | London | £78m | 211 |
| Madge Networks | Will MacDonald | — | Inactive | — | — | — |
| Tokenetic | Robert Dirkin | 2024 | Inactive | Yorkshire and The Humber | — | — |
| BERI Open Systems | — | 2013 | Inactive | East of England | — | — |
| English Language iTutoring | — | 2014 | Inactive | East of England | — | 12 |
| New Leaf Topco Limited | — | 2017 | Inactive | North West | — | 2 |
| Sonic Pi | — | 2018 | Active | Yorkshire and The Humber | — | 2 |
| Contengo | — | 2019 | Active | London | — | 9 |
| Kular | — | 2021 | Active | East Midlands | — | 19 |
| Viriturr | — | 2023 | Inactive | North West | — | — |
| Agathon Limited | — | 2023 | Active | London | — | 1 |
| Recorder | — | 2024 | Active | London | £15m | 4 |
| First AI Talent | — | 2024 | Active | South East | £3m | — |
| OmniBuds | — | 2024 | Active | East of England | £6m | — |
| Trent AI | — | 2025 | Active | London | £34m | — |
| Mosaic Robotics Ltd | — | 2025 | Active | East of England | — | — |
| auryx | — | 2025 | Active | London | £3m | — |
| Lichen AI Ltd | — | 2025 | Active | East of England | — | — |
| AI Sequrity Ltd | — | 2025 | Active | London | — | — |