Cameron exposed in history stumble

He was welcomed on to the Late Show by host David Letterman to the tune of Rule Britannia and dry ice pumping into the studio to replicate a London fog.

And after a brief foray into the issues surrounding Syria and the Arab Spring, Letterman confronted him with the question - who composed Rule Britannia?

A floundering Mr Cameron made a guess at Edward Elgar, only to learn that it was in fact the little-known Thomas Arne, setting words by James Thomson to music.

He also admitted to being stumped when asked for the English translation of Magna Carta - Great Charter - and hesitated a while before naming Runnymede as the location of its signing.

But he immediately named 1215 as the date it was drawn up and was able to give an account of its importance in the birth of democracy - avoiding the famous mistake of comedian Tony Hancock’s character on Hancock’s Half Hour who addressed a jury with the words: “Does Magna Carta mean nothing to you? Did she die in vain?”

Much of Letterman’s questioning appeared designed as an idiot’s guide to Britain for American viewers, as he asked Mr Cameron to name the UK’s four nations.

Mr Cameron had said he would use the show to “bang the drum” for Britain, and raised applause from the audience when he hailed the successful hosting of the Olympics and Paralympics this summer.

But he admitted that he was “not very popular at the moment” - blaming his low ratings on the austerity policies needed to cut the deficit.