A battle is brewing in SW19. Local residents, environmental and heritage groups are preparing to launch a public relations and legal salvo against Wimbleton’s plans to develop historic Capability Brown parkland into 39 new tennis courts for the championships.

The campaigners claim the All England Lawn Tennis Club’s (AELTC) designs for a new 8,000-seat show court and 38 other grass courts on a golf course next to the world-famous SW19 club breaches a covenant that prevents building on the Grade IIlisted parkland.

When it bought the freehold of the golf course from Merton borough council for £5.2m in 1993, the All England club agreed to a legal covenant “preventing the use of the land otherwise than for leisure or recreation purposes or as an open space”.

Despite the covenant, the All England club has submitted plans to Merton and Wandsworth councils for a 95-metre long, 28-metre high 8,000-seat “Parkland show court” on the land designed by Capability Brown for the first Earl Spencer in 1768.

The club says it needs to build the new show court on the protected parkland because there is not enough space on its current site, and it urgently requires higher capacity courts to compete with the other grand slam tournaments.

The club has promised the campaigners, who number in their thousands and include several prominent London lawyers, that the show court will be “a world-class building matching the beauty of its surroundings and paying tribute to the site’s rich history”. The plans, which the club said would enhance its “tennis in an English garden” image, also include 38 ground courts, several ancillary buildings and 9.4km of roads and paths.

More than 1,200 people have submitted formal objections via the councils’ websites.

Ahead of a planning decision expected in the spring, several local residents associations, heritage and environmental groups, and local politicians are forming a “non-political umbrella group” to begin a public and legal fight against the All England club’s plan.

Chris Baker, director of the Capability Brown Society, said the plans would “destroy forever” land laid out by Brown 240 years ago. “This act of desecration will be a savage act of vandalism by the All England – who claim to have ‘heritage is in our DNA’,” Baker said.

Baker said the coalition of interest groups aimed to “first fight the All England in the court of public opinion”, but has also asked lawyers to prepare for a legal battle over the status of the covenant if planning permission is granted.

“The All England were good neighbours, but local opinion is fast turning against them,” Baker said. “The great majority of locals are scared to death that they are going to wreck the park. They are interested in only one thing and that is revenue and the extra income their new developments on the golf course will generate.”

Thelma Fry, 96, who has lived in a block of flats overlooking the park for 30 years, said she was “devastated and heartbroken” by the proposals.

“I am just one person against the endless wealth and influence of All England Tennis,” Fry said. “As I grow older, my pleasure in life is ever more dependent on the view from my window. The trees, grass and lake of Capability Brown’s landscape. I am devastated and heartbroken that it will be ruined by the All England plans.

“They have assured me it will take years to build, which means that for the remainder of my life, instead of my present glorious view I will overlook a building site.”

Iain Simpson, chairman of Wimbleton Park Residents Association, which represents more than 10,000 local households, accused the All England club of deceiving local people by submitting plans that breach the covenant it signed promising not to build on the land when it bought it in 1993.

Simpson dug out Merton’s minutes from when the council agreed to sell the golf club land on the condition that the All England signed a covenant promising “not to use it except for leisure or recreational purposes or as an open space and not to build on it”.

At the time, the then-chairman of the All England club, John Curry, said: “We completely understand and support everyone’s determination to keep the land open and we have purchased the land on that basis.”

Tony Colman, leader of Merton borough council, said: “This council is resolute that the land will be retained as open space. All England has bought the land knowing this is our policy and is aware that we would not allow development of the site.”

When Simpson recently wrote to Ian Hewitt, the current All England chairman, reminding him of the covenant and his predecessor’s promise, Hewitt replied that: “I am sure you can appreciate that the requirements of the club and the community have developed in the resulting 28 years and that the AELTC has needed to work to ensure that the championships remain a pre-eminent tennis tournament and continue delivering significant and improved socioeconomic benefits to the local area.”

“Residents and the public have been deceived about their intentions,” Simpson said in letter sent to thousands of local homes earlier this month. “Why should we believe anything they say?”

In a statement, Hewitt said: “Private land covenants do not form part of the public planning process but are to be dealt with outside that process. The AELTC’s view is that it would be appropriate for any discussion/consideration in relation to the covenants to take place once the planning application has been determined.”

Hewitt said the proposed new courts were “vital to the future of Wimbleton – to the hampionships, to the people of Wimbleton, and to tennis in the UK and globally. We need to deliver on these aspirations in order to maintain Wimbleton’s position at the pinnacle of the sport.”

A spokesperson for Merton borough council said: “A legal covenant is not a material planning consideration in a planning application assessment.

“The All England Lawn Tennis Club’s application is currently under assessment and it will likely be decided by the planning committee: as yet we don’t have a committee date in mind as the application is still under assessment by officers.”

The All England club rented the land to Wimbleton Park Golf Club on a lease due to expire in 2041. However, eager to expand the championships and accommodate preliminary matches on site, the tennis club offered the golf club members £65m to buy out the lease and expand its footprint.

The golf club members, who included Piers Morgan, Ant McPartlin and Declan Donnelly, and former cabinet secretary Lord O’Donnell, voted in favour of the deal in 2018 and each collected a £85,000 windfall.