A 99-year-old actor has threatened to “chain myself to the grounds” of the All England Club if controversial plans to build 39 new tennis courts at Wimbledon are approved on Friday.

Thelma Ruby, who has appeared with Orson Welles and Judi Dench on stage and lives in a flat overlooking the club, said she was determined to take a stand on environmental grounds. Asked whether she was worried about being arrested, Ruby replied: “No, I’m 99. Let them arrest me.”

Speaking at a packed public meeting organised by Save Wimbledon Park, Ruby said that she had been unpersuaded by someone from the “tennis courts” who had tried to change her mind. “I said: ‘What’s going to happen?’” she explained. “He said: ‘Oh, all the trees will be cut down, and there will be eight tennis courts between you and the lake and it’ll take years to build.’

“This beautiful view I get when I look out of my window is not only going to be a building site, but there are going to be polluting lorries passing my window every 10 minutes. And we know, in this day and age, how important trees are. I look several times a day out of the window and enjoy my view. And it gives me strength to carry on.”

The All England Club has argued that it needs a third 8,000-seat show court on the grounds of the old Wimbledon Park golf club, as well as 38 other grass courts that would be used for qualifying and practice, to ensure Wimbledon remains the world’s pre-eminent tennis tournament. However, residents have maintained it will cause environmental damage, take a decade to build, and cause a loss of green spaces on protected metropolitan open land.

Merton council initially approved the plans, but the proposal was referred to the Greater London Authority after Wandsworth council rejected the scheme last November. But the All England Club’s plans appeared to get a huge boost last week when GLA planning officers recommended that conditional planning permission should be granted at a public hearing on 27 September.

However the Liberal Democrat MP Paul Kohler, who represents Wimbledon, told the public meeting that “all is not lost” and they would have a strong case in the courts even if the decision went against them on Friday. He cited a supreme court case, won last year by campaigners in Shrewsbury to stop houses being built on a park protected by a 100-year-old statutory trust, as having relevance.

That message was also echoed by Christopher Coombe, of Save Wimbledon Park. “The GLA stage was always the third set, with Merton the first and Wandsworth the second,” he told the Guardian. “It’s not a done deal. We are just entering the third set tiebreak, and have plenty of aces to serve. The fourth set is the secretary of state and the fifth the courts. We are in it for the long haul.”

The decision will be taken by Jules Pipe, the deputy mayor of London, after the mayor, Sadiq Khan, excused himself from the process having publicly expressed his support for the plans in 2021.