For many start-up founders, being bought by one of Silicon Valley’s giants is a prestigious prize, not to mention a chance to get filthy rich. But when Facebook set out to build Libra, its own cryptocurrency, it struggled to land a willing company among those it approached, even with its massive chequebook in hand.

One source, the founder of a blockchain investment firm who spoke on condition of anonymity, said the social media platform had held talks with 10-12 start-ups. Another, a blockchain start-up founder who also wished to remain anonymous, said the number was significantly higher — the goal being to bring in engineering specialists.