Prime ministers nearing the end of their terms and sinking in the polls tend to have wretched luck. The UK’s Gordon Brown bucked this trend briefly, basking in adulation only a year ago as the man who staved off financial meltdown through a courageous and widely copied plan to recapitalise the banking system.

All the more extraordinary then that Mr Brown is proving so shaky in the area considered his great strength. It is a bit as if a competitor on the TV quiz programme Mastermind keeps on making a hash of his special subject.