President Donald Trump must have thought it could not get any worse, but then it did. James Comey, the FBI Director he fired, waited just a week to serve his revenge dish.

Unlike other scandals this one has potential legal implications for Mr Trump and, as he watched the nightly cable news shows, he will have been appalled to hear the word "impeachment" being bandied around, and experts discussing whether he had committed obstruction of justice.

At the centre of the row over Mr Comey's sacking was a dinner the two men had at the White House in February. Mr Comey, as any member of the FBI might, made a contemporaneous note, known in bureau circles as a "memorandum for the record".

Ultimately, what Mr Trump said to him may be down to interpretation but Mr Comey appears to be in no doubt. He recorded Mr Trump's words in relation to the Michael Flynn investigation as "I hope you let this go".