The surge of mergers and acquisitions means investment banks have become more reliant on deal-related work than at any time since 2008.

Worldwide acquisition-related revenues - fees for advising on deals plus helping finance them through shares or debt - stand at $15.1 billion globally for the year to date, according to Dealogic, equivalent to 42.4% of the total fee pool. That is up from 38.4% in the same period in 2014 and the highest proportion in seven years.