Twelve Extinction Rebellion activists who scaled trees in the Colne Valley nature reserve in west London temporarily prevented High Speed 2 (HS2) contractors from chopping woodland down on Saturday.
The activists spent 10 hours in the trees to raise concern over damage to the environment caused by HS2 development. The direct action successfully halted work at the site, where 16 mature trees were due to be felled.
Environmental activists have set up a camp close to where the works are taking place and have said they are planning similar protests.
Saturday's action was supported by Green Party campaigners, the pressure group Stop HS2 and local residents.
HS2 is a high speed rail link which will connect London, Birmingham, the East Midlands, Manchester and Leeds.