44 Nasstar

Revenue: £93.3m (+53%)

Net profit: -35.3% Staff: 585

This Mayfair Equity-backed Microsoft partner has had a frenetic 2021, rebranding from GCI in March before acquiring Kcom's national IT services business in June. The blockbuster deal propelled its headcount from 700 to 1,200 staff, making it "one of the largest independent providers of managed services in the UK". Although Nasstar quoted a £120m runrate revenue figure even before the Kcom deal, its most recently filed accounts - covering calendar 2019 - show revenues of £93.3m.