It was hardly the best moment for a bombshell. As Alistair Darling expatiated on financial stability in his Mansion House address, all around him in the ornate Egyptian Hall his elite audience was learning via BlackBerries that the top Bank of England official charged with ensuring that stability was to quit.

The shambolic handling of the resignation of Sir John Gieve on Wednesday night was the culmination of months of tension, briefing and bad feeling between the Bank and the Treasury. Yet at that moment of drama, Mervyn King, the Bank governor, was a picture of contentment, seen to give a small smile and a nod as he was handed a note telling him the news about his deputy had leaked.