London-based Sri Lankan refugee Subaskaran Allirajah founded Lycatel in 2004, selling prepaid cards for discount phone calls. In 2006 he launched mobile virtual network operator Lycamobile, leasing capacity from the likes of O2 and Orange to provide customers with no-roaming-charge mobile SIM cards for international calls.
Despite hitting the headlines for its controversial tax arrangements (as well as Allirajah’s donations totaling £420,000 to the Conservative party) Lycatel is now the world's largest cheap international calls network, operating in 16 countries with more than six million users. It made a £6.5m profit on £470.9m sales in 2012-13.
Latest turnover: £613m
Five-year rise in turnover: 89%
No. of employees: 1086
Five-year rise in employment: 209%