Some time ago I had lunch with the chief executive of a well-known company in the City of London. He told me that every time he goes to a dinner party, he turns to the guests either side of him and offers unsolicited feedback on the quality of their conversation during the meal. So, he might tell someone that while he'd enjoyed listening to their views on the Chilcot inquiry, they could have made more eye contact and asked him a few questions. Or that, although he was interested to hear about the choice of schools for their children, they could have kept it briefer or been a little less boastful.

When he told me this I was shocked. How vulgar, I thought. Yet every time I've been out to dinner and sat next to people who were not pulling their weight, I have thought about him and wished that I was brave enough to offer tips on how they could improve.

Last Monday night, I sat next to a senior banker at a large formal function. He was intelligent and had a nice smile, and I thought we were getting along rather well. When coffee had been dispatched, his wife came up to him and asked if he was ready to leave.