Leigh Bolton, director of a small London-based energy and environmental consulting company, is one of the many business users of Skype. Consensia has used it to make phone calls around the world "almost since we first heard about it two years ago", he says.

Although Skype seems at first glance more like a consumer device than a business application, Niklas Zennstrom, the company's co-founder, estimates that 30 per cent of its 40m users are corporate. A lot of the companies using it are small and medium-sized businesses that are saving money by doing do.