21. Software Box (SBL)

Key points

Revenue: £155.5m (+19%)

Net profit: 1.4%

Staff: 126

Known for its strong ties with the Ministry of Defence, this York-based Microsoft and Apple partner has developed its own non-internet-reliant software patch delivery service under the DOBUS brand. SBL enjoyed "strong progress" in its year to 31 August 2017, with revenues soaring 19 per cent to £155.5m and net profits coming in roughly flat at £2.2m. It has 69 services in G-Cloud 10 and references a deal to manage 25,000 mobile devices for DEFRA on its website.