This company runs data centres on the periphery of London — in Enfield, Hayes and Slough, where it is planning to open an additional site next year. Led by chief executive Neil Cresswell, 52, it increased its market share last year, helping sales to hit £23.6m. The London-headquartered business is owned by the property investor Brockton Capital and the Singapore-based technology investor ST Telemedia. In July it received a debt investment of an undisclosed sum from HIG Capital to fund its growth strategy. Its operating-profit margin — 52% — is the highest in the league table.