The Mayor of London has rejected a school’s plans to build a new sports block, despite it being approved by the council.

Harrow School, based in Harrow-on-the-Hill, had hoped to see these facilities serve staff, students and the neighbouring community.

The plans, which would cover 7,300 sq m at the school’s campus, included a science block, games area and car park.

Harrow Council had approved the proposals, noting that they would “benefit Harrow residents” and provide up to 1,400 hours of public leisure use each year.

But Sadiq Khan blocked the application on the basis that it would encroach onto green space known as Metropolitan Open Land.

He argued that, while he supports the school’s desire to develop, he will not sacrifice the principles laid out in his London Plan.

“Since becoming Mayor I have been clear that protecting London’s precious green spaces is one of my top priorities,” he said.

“I absolutely support the school’s ambitions to expand its sporting facilities, and their plans to open them up to the local community for the benefit of people of all ages are to be commended.

“However, I’m clear that expansion of this kind must not encroach on open green space, which is one of the capital’s most important and cherished assets. Nor, in this case, is it necessary to do so, as other options are available.”

Mr Khan noted that almost two-thirds of the planned block would be built on Metropolitan Open Land.

He invited the school’s developers to put forward another application, which would “provide a new facility for their pupils and the community without harming the area’s precious green spaces”.

Both the school and the council expressed their disappointment at the decision; citing the clear, additional advantages to the community as a reason for submitting the plans.

Cllr Keith Ferry, responsible for business, planning and regeneration at Harrow Council, said: “We have worked hard with Harrow School to ensure that their new plans include additional leisure facilities that would benefit Harrow residents, especially considering the high levels of diabetes in our borough.

“We recognise the importance of the Metropolitan Open Land, as well as the Mayor’s drive to protect it, and we agree with his sentiments, but in this case there are special circumstances that override his desires.”

A spokesperson for Harrow School noted the “real need” for such facilities in the area and described it as an “unmissable opportunity”.

The school expressed its gratitude to the council for its support and added that “no decision has been taken as to the next steps” as it seeks guidance from its advisers.