However, increasing numbers of high-profile mass participation events are laying on non-binary categories, in addition to the traditional male and female competitions.

In March, World Athletics banned trans female athletes who had been through male puberty from participating in female elite level competitions. It follows last month’s staging of the London marathon, which included a non-binary category for the first time, as well as a row after a female runner lost her Parkrun record to a transgender woman. Mara Yamauchi, Britain’s third fastest elite female marathon runner, is at the forefront of efforts to highlight the “unfairness” of allowing non-binary categories, which she says effectively offers a second competition opportunity to “men”.

The Information Commissioner is facing calls to act by advocates for fairness in women’s sport after they accused UK Athletics of failing to enforce its own guidance. Marathons that ask entrants to state whether they are non-binary are breaking the law, campaigners have claimed.

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