Have you heard the one about the offensive joke?

There’s no playbook for what to do when faced with this kind of situation, says Alex Czopp, a professor of psychology who has published research on what happens when people speak up about prejudice. “Confrontations are awkward, you are implying . . . that someone has a bias that the vast majority of us are appalled by, some people respond very negatively.” The person might only be dimly aware of my Irishness but if I brought this up then that would be all they would see. Also, he adds: “Humour is almost inherently ambiguous, it’s not meant to be taken seriously.” In fact, I anticipated that if I brought it up, I might be told about distant Irish relatives or friends, all of whom had a much better sense of humour than me and none of whom would have remotely had a problem with this. Very quickly, the problem would be seen as mine.