But it wasn't a joke - to quote the Beeb article:
"I did mean the part about having trouble with girls," he said. "It is true that people - I have fallen in love with people in the lab and people in the lab have fallen in love with me and it's very disruptive to the science because it's terribly important that in a lab people are on a level playing field.
I found that these emotional entanglements made life very difficult.
I'm really, really sorry I caused any offence, that's awful. I certainly didn't mean that. I just meant to be honest, actually.
He also said they were meant in a 'light-hearted' way but I'm not sure how - he was given the opportunity to retract them, or claim they'd been taken out of context, but all he appears to have apologised for is saying them where journos could hear. Hardly the bloody point.
He needs to take it like a grown up. He said what he said, he confirmed that he meant what he said. He was presumably informed by UCL that his comments were not in keeping with their ethos and so he resigned.