Save Wimbledon Park has taken the legal action against the Greater London Authority over its decision to allow the All England Club to expand.
The campaign group claims the move is unlawful because the former golf club land is legally protected under a covenant.
But the GLA and All England Club dispute the restrictions exist.
The plans were first submitted to both Merton and Wandsworth councils in 2021, after the All England Club bought out golf club members.
Merton Council approved the plans while Wandsworth didn’t, meaning the decision was left to London’s Mayor, Sadiq Khan.
He had to excuse himself after previously expressing support for the plans and they were eventually given the go ahead by the deputy Mayor for planning.
The hearing continues.
