David Cameron was subjected to a bizarre quiz on British culture and history as he appeared on one of the USA's most influential TV chat shows.
The Prime Minister was welcomed on to the Late Show by host David Letterman to the tune of the house band playing 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 - the subject of his speech to the United Nations earlier in the day - Letterman confronted him with a truly tough question - who composed Rule Britannia?
A floundering Mr Cameron made a guess at Edward Elgar, only to learn from Letterman's researchers 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.
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 four nations of the UK. "What is the deal on Wales?" asked Letterman. "Did they vote for you, the people of Wales?" "Some of them did," replied Mr Cameron - and explain the difference between Northern Ireland and the Republic.
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, perhaps diplomatically, ignored an apparent dig by Letterman at Republican presidential candidate Mitt Romney, who famously questioned if London was ready for the Olympics. "The idea that two major world class athletics events took place in London... who would have bet against that going off flawlessly, as it seems to have done?" joked Letterman.
Mr Cameron also boasted of his government's efforts to create a good environment for investment in the UK and about the creation of one million private sector jobs over the past two years. 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.
Asked how he rated his performance on the Letterman show, Mr Cameron said: "I'm a history obsessive, so I'm sorry I didn't do better. I think, when I get home and do my children's homework, maybe I need to sit down and do a little bit extra myself."