Folding his 6ft 7in frame into a small office chair at the headquarters of iZettle on Kungsgatan in central Stockholm, Jacob de Geer takes issue with the notion that start-ups have mushroomed in the city overnight.

Many of today's tech successes have roots in the dotcom bubble 15 years ago, de Geer argues, and he should know - he was there. In 1999, at the height of the bubble, he joined Tradedoubler, a Stockholm-based ad-sales platform, as one of its first employees. His boss was Martin Lorentzon, better known today as the co-founder of music-streaming service Spotify.