In search of a European Google

California's Silicon Valley runs the show when it comes to successful tech companies. So why has the old world failed to produce a thriving digital industry to rival the US?

David Galbraith, a partner at venture investment firm Anthemis, has a statistic he likes to quote. "The combined value of the top three internet companies in the Americas - so, basically, in America - is around $0.75tn (0.5tn). In Asia, it's around $0.5tn. In Africa, it's $50bn. And in Europe, it's just $25bn."

When I first heard the figure from him, on the hottest day of the year at a conference in the City of London, I was shocked. Galbraith, who helped create both net standard RSS and listings site Yelp in the early 2000s, is not known for exaggeration.