Legal challenge over trans people using women's changing rooms at Hampstead Heath swimming ponds to continue

The organisation had been challenging the corporation's policy permitting trans individuals to use facilities corresponding to their gender identity, arguing this constitutes sex discrimination.

Mrs Justice Lieven had previously blocked the judicial review in January, ruling that the county court was the "appropriate forum" rather than the High Court.

Sex Matters subsequently sought appeal permission, contending the judge had erred in law.

The legal action follows last year's Supreme Court judgment establishing that biological sex at birth determines a person's legal sex.

Lady Justice Elisabeth Laing stated that the original judge "did not engage with the merits of the grounds for judicial review except at the end of her judgment".

She further concluded it was "arguable" that elements of Mrs Justice Lieven's decision contained errors, including her finding that the claim had been submitted outside the permitted timeframe.

Tom Cross KC, representing Sex Matters, had argued in written submissions that the refusal to allow the challenge was "plainly wrong".

The barrister maintained it was "contrary to the public interest, the rule of law, and the sound administration of justice" for these matters to remain unexamined by the High Court.

A fresh hearing date will be scheduled by the High Court in London in due course.

Maya Forstater, chief executive of Sex Matters, expressed her satisfaction with the outcome.

"Her ruling in the Court of Appeal confirmed that as a specialist charity with objections focused on the sound administration of the law in relation to sex, Sex Matters has standing to take this case," Ms Forstater said.

She emphasised the broader significance of the litigation, stating: "This case will have implications for single sex provision all over the country".

Ms Forstater criticised ministers for failing to issue revised regulatory guidance since the Supreme Court's landmark decision, arguing this had provided "businesses and service providers an excuse to continue flouting the law on single sex provision as clarified by the country's most senior judges".

She added that a favourable High Court ruling "would demonstrate that failing to comply with the law has consequences".

A spokesman for the City of London Corporation, which oversees Hampstead Heath as a registered charity, indicated the organisation would mount a robust defence.

"We note the decision and will continue to contest this case vigorously," the spokesman said, adding that ongoing litigation was diverting "significant time and resources" away from managing the heath and delivering public services.

The corporation pointed to its recent public consultation, in which more than 38,000 people participated over two months, with 86 per cent backing the existing trans-inclusive arrangements.

Among respondents, 84 per cent had previously swum at the ponds, and 74 per cent were London residents.

The consultation examined six potential options for the Kenwood Ladies, Highgate Men's and Hampstead mixed ponds, with 86 per cent opposing strict single-sex access.