The old Eton College sanatorium has been sold to a developer despite a campaign by neighbours to save it.

The building adjoins Stonebridge Field and is known as the Sandles. It is not listed and has not been used as a sanatorium for decades.

But neighbours say it is an important part of the landscape and campaigner Patrick McGlynn launched a bid to save it last year describing it as an ‘extremely atmospheric building that has a real presence to it.’

Now Eton College has sold it to property developer Leon Lenik who has applied to demolish the building and the neighbouring Rose Cottage, putting 11 three-storey detached four bedroom homes on the site.

But opposition is growing as members of Eton Town Council agreed to oppose the plan when they met on Thursday.

The heritage group Windsor and Eton Society’s environment committee also decided on Monday that the planned houses would be too densely packed and would overlook neighbours.

But they did not oppose in principle the demolition of the Sandles. English Heritage has also refused to support the retention of the Victorian building. The final decision will rest with Royal Borough planning councillors, who will consider Mr Lenik’s plan within the next two months.

This week the new owner stood up for his plan. Mr Lenik is the man behind the recent Windsor Bridge Court development on the Eton side of the bridge. He said: “I like to be proud of what I do. The homes I am proposing will not be as tall as the building that is there already. I took extensive advice and have agreed to protect the Lebanese cedar tree among others and will be landscaping the area adding more trees. It should be very attractive.”

The building was used for accommodating college staff when the college’s sanatorium moved to part of St John the Evangelist Church in 1981.