Downing Street insisted it would be “calm and orderly”. But on Tuesday night the banking system was buckling, the taxpayer was poised to launch an emergency bail-out and recriminations were flying between Westminster and the City over who was to blame for the shambles.

After a day of carnage on the stock market, Gordon Brown had no choice but to sanction a move few modern politicians could ever have imagined implementing: the part-nationalisation of British banks, through a taxpayer-backed recapitalisation scheme.