| Auden Mckenzie and Actavis UK | Intas Pharmaceuticals Ltd. | pharmaceuticals | 2023 | UK-CMA | £130,000,000 |
| British Telecommunications plc | BT | telecommunications | 2012 | UK-OFCOM | £117,042,000 |
| Pfizer Limited | Pfizer | pharmaceuticals | 2022 | UK-CMA | £63,300,000 |
| British Airways | International Airlines Group | airlines | 2012 | UK-OFT | £58,500,000 |
| Facebook | Meta Platforms Inc. | information technology | 2021 | UK-CMA | £50,500,000 |
| Royal Mail plc | International Distributions Services PLC | miscellaneous services | 2018 | UK-OFCOM | £50,000,000 |
| British Telecommunications plc | BT | telecommunications | 2017 | UK-OFCOM | £42,000,000 |
| Advanz Pharma | Nordic Capital | private equity (including portfolio companies) | 2021 | UK-CMA | £40,900,000 |
| Cinven | Cinven Group | private equity (including portfolio companies) | 2021 | UK-CMA | £37,100,000 |
| Mastercard | MasterCard | financial services | 2022 | UK-PSR | £31,560,062 |
| Royal Bank of Scotland Group plc | NatWest Group PLC | financial services | 2011 | UK-OFT | £28,590,000 |
| FP McCann Limited | FP McCann Limited | construction and engineering | 2020 | UK-CMA | £25,449,676 |
| GlaxoSmithKline plc and GlaxoSmithKline UK Ltd. and SmithKline Beecham Ltd. and Beecham Group plc | GlaxoSmithKline | pharmaceuticals | 2016 | UK-CMA | £22,000,000 |
| Erith Contractors Ltd and Erith Holdings Ltd | | | 2023 | UK-CMA | £17,568,800 |
| Keltbray Ltd and Keltbray Holdings Ltd | | | 2023 | UK-CMA | £16,000,000 |
| Vp plc | | | 2020 | UK-CMA | £11,235,660 |
| Sainsbury's Supermarkets Limited and J Sainsbury plc | J Sainsbury PLC | retailing | 2011 | UK-OFT | £11,040,000 |
| Reckitt Benckiser Healthcare (UK) Ltd. and Reckitt Benckiser Group plc | Reckitt Benckiser | household and personal care products | 2011 | UK-OFT | £10,175,000 |
| Aspen Pharmacare Holdings Ltd. et al. | | | 2020 | UK-CMA | £10,101,954 |
| Asda Stores Ltd. and Asda Group Ltd. and Wal-Mart Stores (UK) Ltd. and Broadstreet Great Wilson Europe Ltd. | EG Group | retailing | 2011 | UK-OFT | £9,100,000 |
| T. E. Scudder Ltd | | | 2023 | UK-CMA | £8,256,264 |
| H.J. Enthoven Limited and Eco-Bat Technologies Limited | | | 2020 | UK-CMA | £8,076,504 |
| Alliance Pharmaceuticals Limited and Alliance Pharma plc | Alliance Pharma PLC | pharmaceuticals | 2022 | UK-CMA | £7,900,000 |
| Stanton Bonna Concrete Limited et al. | | | 2019 | UK-CMA | £7,474,745 |
| Focus Pharmaceuticals Limited and Mercury Pharma Group Ltd. and Concordia Investments (Jersey) Ltd. and Advanz Pharma Corp. Ltd. et al. | Nordic Capital | private equity (including portfolio companies) | 2022 | UK-CMA | £7,288,853 |
| Dairy Crest Limited and Dairy Crest Group plc | Saputo | food products | 2011 | UK-OFT | £7,140,000 |
| Lexon (UK) Limited | Bestway Healthcare | healthcare services | 2022 | UK-CMA | £6,706,220 |
| Flynn Pharma Limited | | | 2022 | UK-CMA | £6,704,422 |
| Tesco Stores Limited and Tesco Holdings Limited and Tesco plc | Tesco PLC | retailing | 2013 | UK-OFT | £6,500,000 |
| BT Group plc | BT | telecommunications | 2020 | UK-OFCOM | £6,300,000 |
| HGCapital | Hg Capital | private equity (including portfolio companies) | 2021 | UK-CMA | £6,200,000 |
| Generics (UK) Ltd and Merck KGaA | | | 2016 | UK-CMA | £5,841,286 |
| Safeway Stores Limited and Strores Group Limited and Safeway Limited | Clayton Dubilier & Rice | private equity (including portfolio companies) | 2011 | UK-OFT | £5,690,000 |
| John F Hunt Ltd and John F Hunt Group Ltd | | | 2023 | UK-CMA | £5,600,000 |
| Roland (U.K.) Limited and Roland Corp. | | | 2021 | UK-CMA | £5,004,151 |
| Cinven Capital Management (V) GP Ltd. and Cinven Partners LLP et al. | Cinven Group | private equity (including portfolio companies) | 2022 | UK-CMA | £4,856,620 |
| Fender Musical Instruments Europe Ltd. and Fender Musical Instruments Corp. | | | 2020 | UK-CMA | £4,531,185 |
| JD Sports | JD Sports Fashion | retailing | 2022 | UK-CMA | £4,320,000 |
| Area Sq Ltd. and Cube Interior Solutions Ltd. and Fourfront Group Ltd. and Fourfront Holdings Ltd. | | | 2019 | UK-CMA | £4,143,304 |
| CPM Group Limited | Marshalls PLC | building materials | 2019 | UK-CMA | £4,000,000 |
| M.G.F (Trench Construction Systems) Ltd | | | 2020 | UK-CMA | £3,773,910 |
| McGee Group (Holdings) Ltd | | | 2023 | UK-CMA | £3,766,278 |
| Casio Electronics Co. Ltd. and Casio Computer Co., Ltd. | Casio Computer Co. | miscellaneous manufacturing | 2019 | UK-CMA | £3,695,535 |
| Medreich plc and Medreich Ltd and Meiji Seika Pharma Co. Ltd and Meiji Holdings Co. Ltd. | Meiji Group | food products | 2022 | UK-CMA | £3,452,446 |
| Robert Wiseman & Sons Limited and Robert Wiseman Dairies plc | | | 2011 | UK-OFT | £3,200,000 |
| British Telecommunications plc | BT | telecommunications | 2013 | UK-OFCOM | £2,896,800 |
| Auden Mckenzie (Pharma Division) Ltd. and Accord-UK Ltd. | Intas Pharmaceuticals Ltd. | pharmaceuticals | 2020 | UK-CMA | £2,882,238 |
| CPL Distribution Limited and CPL Industries Holdings Limited | | | 2018 | UK-CMA | £2,816,514 |
| The National Lighting Co. Ltd. and Saxby Lighting Ltd. and Endon Lighting Ltd. and Poole Lighting Ltd. | | | 2017 | UK-CMA | £2,763,000 |
| Copart, Inc. and CPRT LLP and Copart UK Ltd. | Copart Inc. | information services | 2023 | UK-CMA | £2,500,000 |
| Waymade Plc | | | 2021 | UK-CMA | £2,500,000 |
| Brown and Mason Group Ltd | | | 2023 | UK-CMA | £2,400,000 |
| ITW Limited | Illinois Tool Works | industrial equipment | 2016 | UK-CMA | £2,298,820 |
| Franklin Hodge Industries Ltd. and Carter Thermal Industries Ltd. | | | 2016 | UK-CMA | £2,015,135 |
| Squibb Group Ltd. | | | 2023 | UK-CMA | £2,000,000 |
| Cantillon Ltd and Cantillon Holdings Ltd | | | 2023 | UK-CMA | £1,920,000 |
| Focus Pharmaceuticals Limited and Mercury Pharma Group Ltd. and Cinven Partners LLP et al. | Nordic Capital | private equity (including portfolio companies) | 2022 | UK-CMA | £1,843,380 |
| ThirdWay Interiors Ltd. and The ThirdWay Group | | | 2019 | UK-CMA | £1,780,703 |
| Lactalis McLelland Limited | Lactalis | food products | 2011 | UK-OFT | £1,660,000 |
| Heathrow Airport Ltd. and Heathrow Airport Holdings Ltd. | Heathrow Airport Holdings | miscellaneous services | 2018 | UK-CMA | £1,600,000 |
| Actavis UK Ltd. | Intas Pharmaceuticals Ltd. | pharmaceuticals | 2016 | UK-CMA | £1,542,860 |
| Associated Lead Mills Limited and Royston Sheet Lead Limited and International Metal Industries Limited | | | 2020 | UK-CMA | £1,510,228 |
| Thomas Armstrong (Timber) Ltd. and Thomas Armstrong (Holdings) Limited | | | 2017 | UK-CMA | £1,509,000 |
| Korg (UK) Ltd. and Korg Inc. | | | 2020 | UK-CMA | £1,504,707 |
| Dar Lighting Ltd and Castlegate 624 | | | 2022 | UK-CMA | £1,500,000 |
| Meta Platforms, Inc. and Tabby Acquisition Sub Inc. and Facebook UK Ltd. | Meta Platforms Inc. | information technology | 2022 | UK-CMA | £1,500,000 |
| Sepura | | | 2022 | UK-OFCOM | £1,500,000 |
| Mercedes-Benz UK Limited and Daimler UK Limited and Daimler AG | Mercedes-Benz Group | motor vehicles | 2013 | UK-OFT | £1,492,646 |
| JD Sports Fashion Plc | JD Sports Fashion | retailing | 2022 | UK-CMA | £1,485,000 |
| Ping Europe Limited | | | 2017 | UK-CMA | £1,450,000 |
| DSM Demolition Ltd et al. | | | 2023 | UK-CMA | £1,400,000 |
| The Cheese Company Ltd. and Waterford Foods International Ltd. and Glanbia Investments (UK) Ltd. and Glanbia (UK) Ltd. | | | 2011 | UK-OFT | £1,260,000 |
| Lexon (UK) Limited | Bestway Healthcare | healthcare services | 2021 | UK-CMA | £1,220,383 |
| Spire Healthcare Ltd. and Spire Healthcare Group plc | Spire Healthcare PLC | healthcare services | 2020 | UK-CMA | £1,200,000 |
| Berendsen Cleanroom Services Ltd. fka Micronclean (Newbury) Ltd. and Berendsen plc | | | 2017 | UK-CMA | £1,197,956 |
| Medreich plc and Medreich Ltd | Meiji Group | food products | 2022 | UK-CMA | £1,167,554 |
| Loop Interiors London LLP and Loop Interiors Ltd. | | | 2019 | UK-CMA | £1,090,816 |
| Focus Pharmaceuticals Ltd. and Focus Pharma Holdings Ltd. and Mercury Pharma Group Ltd. | Nordic Capital | private equity (including portfolio companies) | 2022 | UK-CMA | £921,357 |
| Prepaid Financial Services Limited | | | 2022 | UK-PSR | £916,746 |
| Leicester City Football Club Limited | | | 2023 | UK-CMA | £880,000 |
| Ultra Finishing Limited | | | 2016 | UK-CMA | £786,668 |
| Advanced Payment Solutions | | | 2022 | UK-PSR | £755,419 |
| Thomas Armstrong (Timber) Ltd. and Thomas Armstrong (Holdings) Limited | | | 2017 | UK-CMA | £684,000 |
| Ciceley Commercials Limited and Ciceley Limited | | | 2013 | UK-OFT | £659,675 |
| E (Gas and Electricity) Ltd | | | 2019 | UK-OFGEM | £650,000 |
| Fuel Express Ltd. and Fuel Express (Bagnalls) Ltd. and Carbo (UK) Ltd. and G.N. Grosvenor Ltd. | | | 2018 | UK-CMA | £627,867 |
| Hoffman Thornwood Ltd. and Consolidated Timer Holdings Ltd. | | | 2017 | UK-CMA | £625,000 |
| Lexon (UK) Limited and Lexon UK Holdings Limited | Bestway Healthcare | healthcare services | 2022 | UK-CMA | £593,780 |
| Galglass Ltd. Irish Industrial Tanks Ltd. and Kernoff Ltd. | | | 2016 | UK-CMA | £587,926 |
| Hamptons Estates Ltd. and Countrywide plc and Countrywide Group plc | | | 2015 | UK-CMA | £582,455 |
| Focus Pharmaceuticals Limited and Focus Pharma Holdings Limited | Nordic Capital | private equity (including portfolio companies) | 2022 | UK-CMA | £549,343 |
| Micronclean Ltd. fka Fenland Laundries Ltd. | | | 2017 | UK-CMA | £510,118 |
| Storm Model Management Limited and Storm Models Limited | | | 2016 | UK-CMA | £491,000 |
| Elite Sports Group Limited and Elite Corporation Limited | | | 2022 | UK-CMA | £459,000 |
| Clifford Devlin Ltd | | | 2023 | UK-CMA | £423,615 |
| Footasylum | | | 2022 | UK-CMA | £400,000 |
| Models One Ltd. and One Worldwide Ltd. and Models 1 New Co Ltd. | | | 2016 | UK-CMA | £394,000 |
| Consultant Eye Surgeons Partnership (CESP) Ltd. | | | 2015 | UK-CMA | £382,500 |
| Hamsard 3149 Ltd. and Quantum Pharmaceutical Ltd. and Total Medication Management System dba Tomms Pharmacy | | | 2014 | UK-OFT | £370,226 |
| Enza Motors Limited and Enza Holdings Limited and Enza Group Limited | | | 2013 | UK-OFT | £347,198 |
| ION Investment Group Limited and ION Trading Technologies Limited | | | 2021 | UK-CMA | £325,000 |
