There are some questions that would be fatal for a serving British prime minister not to know the answer to. The composer of Rule Britannia is not one of them.
So while David Cameron may have joked to David Letterman last night that his career was now “ended” for getting that wrong, he should count himself lucky to have got through the US talk-show programme without any serious glitches.
The Letterman Show is not exactly Newsnight with Paxman – politicians are teased and prodded rather than skewered and grilled. But with 3m viewers, including most of the UK media, it was fairly risky for Cameron to become the first serving PM to go on the show.
Yes, he failed to identify Thomas Arne as composer of one of the big Last Night of the Proms anthems. (He incorrectly guessed Edward Elgar, who was around 150 years later.) And he didn’t know the literal translation of Magna Carta.
This will have gone over the heads of most American viewers; the reaction of many – as shown by the BBC at least – was broadly positive.
In fact the prime minister correctly answered many of the elements of what my colleague Andrew Edgecliffe-Johnson described as an “eccentric citizenship test”.
Cameron was articulate, good-natured, smooth, polished and of course “well-spoken”. (Not that all Americans can distinguish between Eton vowels and estuary English.)
This was the “good” Cameron, as opposed to the “bad” Cameron – an over-bearing, arrogant bully – who not infrequently emerges during Wednesday’s Prime Minister’s Questions.
He also managed to fit in many of his pre-prepared lines about Britain being open for business, and the successful Olympics and Paralympics.
The over-riding memory of the performance may be the wrong answers, not least because that’s what the BBC is leading its reports on.
In fact the show covered lots of other ground including the empire, Wales, the euro, the difference between Ireland and Northern Ireland and Larry the Cat who lives at Downing Street.
There was nothing about Mr Cameron’s recent travails (although he admitted he was not popular), his ranting chief whip, or the worsening UK economy. This was more a getting-to-know you session between the PM and an audience many of whom believe Blair is still running Britain.
Was he as witty as Boris Johnson, who went on the show this summer? No. But that should not be seen as a problem for him. Cameron’s own assessment? “I think there were some good bits, and some less than good bits”.
He didn’t leave the audience in stitches, or baying for more, but neither did he alienate them. The highlight, from Downing Street’s perspective at least, will be the huge claps when he criticised the unlimited use of advertising by US political parties, which will see billions of spending on the current elections. So not so bad.