The Mayor's Office is due to make a decision today on whether or not a waste burning incinerator can be built in Sutton.
If given the go ahead the incinerator will burn waste from four London boroughs (Croydon, Kingston upon Thames, Merton and Sutton).
Local campaign groups, and Green Party members of the London Assembly are opposed to the plan.
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Three Tory rebels and three Labour defectors who stood against their old parties were all defeated last night.
The Lib Dems balanced their London losses by snatching Richmond Park from the Tories. Sarah Olney won the seat from Zac Goldsmith.
It was a bad night for the Liberal Democrats - Chuka Umunna, Luciana Berger and Sam Gyimah all failing to get elected.