Jo Swinson has had a dreadful general election campaign. But the Liberal Democrat leader has at least succeeded in catapulting one of her party’s principal policies up the national agenda even if many of her supporters may now wish she hadn’t. In an interview on BBC Radio Five Live yesterday she found herself stumped for an answer to a caller who asked “what is a woman?”. That followed an equally difficult interview on the Today programme on Radio 4 when she was asked whether she accepted that biological sex existed. “I don’t think things are as binary as is often presented,” she replied.

The source of Ms Swinson’s difficulties is her party’s proposal to reform the Gender Recognition Act, which requires an individual to satisfy