Bailiffs have begun evicting a group of squatters who have been occupying a site near Heathrow Airport in protest at the airport's expansion.
The group formed a community garden called Grow Heathrow on the derelict site near Sipson, Hillingdon, in 2010.
High Court enforcement officers and police arrived to clear the area early on Tuesday morning and have so far secured about half of the site.
Nevertheless, protesters have said they plan to remain "indefinitely".
A number of legal battles have been held over the privately-owned land since it was taken over, with the latest proceedings going against Grow Heathrow.
The group moved on to the site in March 2010 and turned an area which was neglected and attracted anti-social behaviour problems into a community garden where some of them lived.
Once bailiffs arrived, protesters chained themselves to structures including a wind turbine tower and inside an underground tunnel.
BBC London correspondent Tom Edwards, who is at the site, said he had been told by protesters that they were still preparing for the site's ninth birthday party to be held next month.
Terry, who lives in nearby Hayes and has been a supporter of the garden for the last nine years, said enforcement officers had "caught them a little bit off guard".
He said the plot had been set up "against the third runway and what they're doing around here."
Last year ministers gave their backing for the creation of a third runway, which Heathrow Airport has said will create about 60,000 new jobs and generate about £70bn in total economic benefits.
The Met Police said officers and a police helicopter were at the site "to prevent a breach of the peace".