David Cameron's British history knowledge put to the test on the Late Show with David Letterman

Ouch! David Cameron may regret ever appearing on the Late Show with David Letterman. He was ambushed by the host who had the British Prime Minister take part in a quiz on British history.

And, yes, he flunked it. Cameron even joked at the end: "That is bad - I've ended my career on your show tonight."

But hold on. Here is the surprising thing. The audience loved Cameron.

Every single person I spoke to as they left the theatre in New York where the show is recorded gave the Prime Minister the thumbs up.

They thought he was amusing and charming. I repeatedly asked people to rate Cameron's performance. Most gave him 10 out of 10. The worst I could get was an "8".

That may not change the "PM is left red-faced" headlines that are sure to be in the British newspapers this morning. But it means he played well in the American heartland, which after all was the target audience.

Here's the only conclusion I can draw: Americans are a very forgiving lot.