David Cameron stumped by US show host's quiz

Cameron appeared on Letterman's 'Late Show'. The house band played "Rule Britannia" as he walked on stage, the Daily Mail reported.

Letterman, famed for his wit, tested Cameron with questions on British history.

Asked who composed "Rule Britannia", Cameron replied: "You are testing me there. Elgar, I will go for."

Letterman, however, revealed the music was written by Thomas Arne to a poem by James Thomson.

The prime minister did better on the Magna Carta, correctly answering that it was signed in 1215 at Runnymede.

But, he was stumped when asked for a literal translation of the Latin name that means "Great Charter", the daily said.

"It would be good if you knew this," Letterman said, to which Cameron replied: "Yes, it would. You've found me out. I've ended my career on your show tonight!"

Cameron correctly identified the population of Great Britain and the countries that make it up.

Asked whether he was popular in his country, Cameron said: "Not very popular, no. We have got this budget deficit - we have to make difficult decisions and that makes you unpopular."