David Cameron is no stranger to fielding pressing questions, regularly absorbing the stress of parliamentary interrogations.
But when US chat show king David Letterman surprised him with a general knowledge quiz, his cool confidence wavered.
The Prime Minister, who was in New York for a meeting at the UN, made history by becoming the first serving British leader to warm up the hot seat of the popular show.
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The host was suitably flattered, welcoming his guest by having the house band strike up a thundering rendition of Rule Britannia. He then fired off a round of questions designed to test the premier's grasp of history.
Asked who had composed Rule Britannia, Mr Cameron was at a loss: "You are testing me there. Elgar, I will go for."
The music was in fact composed by Thomas Arne.
Britain's leader did briefly redeem himself by correctly identifying that the Magna Carta – one of the most important documents in British history – was signed in 1215 at Runnymede.
He floundered again though when asked to translate the document's Latin title, with David Letterman teasing "It would be good if you knew this,"
Unfortunately the translation – Great Charter – wasn't part of the former Etonian's repertoire.
"You've found me out. I've ended my career on your show tonight!" he exclaimed.