Founder Greg Burgess, 33, set up this company in 2014 with a £50,000 loan. He paid it off in its first year and the company has been profitable ever since. It serves up to 7,000 ads a second across a portfolio of search, price comparison and media websites that attract a combined 100 million page views every month, while its software finds trends and capitalises on them fast. Google, eBay and Microsoft are among its key advertising customers. Sales grew to £8.6m last year, two thirds of which came from overseas.