It's embarrassing enough to be overheard being rude about your neighbour if it's just the guy from down the road when you're mouthing off in the pub. Consider how much worse for David Cameron.
Only a few months ago he was making cheery political hay by promising to roll out the red carpet for the tax exiles who would doubtless pour across the Channel should the Socialists prevail in France, and making droll little asides about cheese duties, to boot.
And there, yesterday, was the new President François Hollande himself, on his first official visit to the UK, and in private, one can't help but assume, wearing roughly the same facial expression Mr Jones from 31A might shortly after hearing you cracking jokes about what a mess he was making of his front garden.
Hollande and Cameron got through it; they have to, after all, and politicians are by and large sufficiently used to the political fray to know that such barbs are of limited significance. (Mr Cameron's rapprochement with Nick Clegg is, of course, a case in point.)
But it can't be easy. And there are plenty of examples of diplomatic relations that have been undermined by nothing more profound than the personal animosity between two leaders, which is one of the reasons it's generally considered good form to avoid taking sides in your allies' domestic political races. So you have to ask: what made Mr Cameron do it?
It may be something to do with his general inability to resist having a good kick at any political adversary who appears to have fallen on hard times – an instinct that has rarely displayed him to his best advantage in the House of Commons, and plays little better on the international stage.
One hesitates to say it, but he should learn from Tony Blair. Blair's chameleon-like political persona was not without its drawbacks, but it did allow him to cut a convincing figure as a statesman. The results might have been disastrous, but you have to admire his ability to form an alliance with George Bush, an American president who was his political opposite in every way except the one he decided mattered.
Now Mr Cameron must try to find common cause with a French President who will presumably not view his attempts at conciliation with any great enthusiasm. He had better hope he is able to do so. Whether he likes it or not, he is saddled with a Socialist across the Channel for the rest of this parliament. He might find things easier if he could refrain from taking the mickey out of him.