Revenue: £45.5m (+16%)
Net profit margin: 12.7% Staff: 232
Boasting a total co-location and cloud capacity of circa 1,500 racks, this Derby-based datacentre ace last month won a contract to replace Stagecoach's legacy WAN infrastructure with a new SD-WAN architecture. In its year to 31 March 2019, Node4 racked up net profits of £5.8m on revenues of £45.5m. It recently made the fifth and largest acquisition in its history in the shape of virtual private cloud provider Secura.