In 2009, a single email may have helped reshape British banking policy. Documents released by the US Department of Justice this year appear to show Jeffrey Epstein — the disgraced financier and convicted sex offender — asking former UK minister Peter Mandelson whether JP Morgan's chief executive, Jamie Dimon, should personally lobby Chancellor Alistair Darling to abandon a proposed tax on banker bonuses. Mandelson, according to the files, replied that Dimon should "mildly threaten" the chancellor. Dimon is subsequently reported to have done exactly that, allegedly warning Darling that JP Morgan — a major employer in Britain and a significant purchaser of UK government bonds — might cancel plans for a new London headquarters.

That sequence of events is now at the centre of a formal congressional inquiry. Senator Elizabeth Warren, the leading Democrat on the Senate Banking Committee, wrote to Dimon last week demanding that he clarify the full extent of his interactions with Epstein. "It is critical that Congress and the American public fully understand the extent of any interactions the bank and you had with Epstein," Warren stated in the letter, which was published by the committee on Monday and first reported by the Financial Times. The inquiry carries particular weight because Dimon testified in court in 2023 that he had never met Epstein and had not heard the man's name until Epstein's arrest in 2019.

The pressure on Dimon has been compounding since then. Jes Staley, the former JP Morgan executive who later ran Barclays, has alleged that he discussed the bank's relationship with Epstein directly with Dimon — a claim JP Morgan flatly denies, noting that a UK tribunal already found Staley's testimony "evasive and unreliable." Mandelson, for his part, was dismissed as US ambassador to the United Kingdom last September after his close ties to Epstein became public.