James Carville, adviser to President Bill Clinton, once said that were he reincarnated, he would choose to return as the bond market: he could then intimidate anyone.

There is little doubt of the reality of such intimidation. In its manifesto for the 2010 UK general election, the Conservative party listed a series of “economic benchmarks for Britain”. Top of the list: “We will safeguard Britain’s credit rating .” The following year, President Nicolas Sarkozy was reported to have told aides “if France loses its triple A rating, I’m dead”. A few days later France lost that status; a few months later, Mr Sarkozy was out of office.

A sovereign credit rating supposedly reflects the likelihood that a country will default on its government debt. But is Britain or France likely to default? And should their governments care what Moody’s, Standard & Poor’s or bond traders think, anyway?