Near the peak of the last stock market boom in February 2007, a letter arrived at the Amsterdam headquarters of ABN Amro that was to change the course of Europe’s banking industry.

The Children’s Investment Fund (TCI), a London hedge fund run by Sir Chris Hohn, was demanding the Dutch bank put itself up for sale. “We believe that it would be in the best interests of all shareholders . . . to actively pursue the potential break-up, spin-off, sale or merger of its various businesses,” wrote Patrick Degorce, a TCI partner.

That intervention triggered a domino effect that ultimately led to the collapse of the world’s biggest bank, Royal Bank of Scotland. RBS bought ABN in a £50bn deal later in 2007. When the