Martina Navratilova is one of the last people you’d expect to be accused of intolerance. Arguably still the world’s most famous lesbian, the tennis player neither concealed nor apologised for her sexuality at a time when many gay people were afraid to come out to family, never mind a global sporting audience. She also gave a coaching job to Renée Richards, a player on the women’s circuit who was born Richard Raskind.

This week, Navratilova was sacked by Athlete Ally, a US campaign for lesbian, gay, bisexual and transgender (LGBT) people in sport. The group has accused her of “transphobia” for questioning whether a transgender woman, born and raised male and retaining a full male body, should be allowed to compete in women’s sport simply because they have taken drugs to reduce their testosterone levels.

That meets the criteria of many sporting authorities, but troubles a lot of people, including Navratilova. They note that underlying male biology means transgender women build up muscle mass, height and reach, giving them advantages that cannot be erased by changing their hormones.