HS2 has begun evicting a group of environmental protesters who have been living at a camp along the route of the rail project for more than two years.

Dozens of police and bailiffs are at the Harvil Road site in the Colne Valley, in the London borough of Hillingdon.

The protesters are opposing the eviction and claim HS2 and the bailiffs are acting unlawfully as they have not served the demonstrators with high court eviction notices ordering them to vacate the land.

Three protesters have been arrested at the camp, which was established in October 2017. Since then, groups of environmental protesters, many from the Green party and Extinction Rebellion, have been a permanent presence on the site, monitoring HS2’s work and documenting what they say is the destruction of flora and fauna.

Opponents of HS2 have pointed to its spiralling costs and the destruction of trees and wildlife to make way for the rail line.

The Colne Valley nature reserve is home to a variety of fauna and flora including bats, owls and osprey. Protesters claim that pile-driving into an aquifer (an underground layer of water-bearing permeable rock) on the site, which supplies almost a quarter of London’s water, will cause serious damage to this water supply. HS2 denies there will be any damage.

A report from Lord Berkeley, a dissenting member of a panel reviewing the HS2 project, claims the costs are “completely out of control”.

It is understood HS2 is carrying out two different kinds of enforcement action on the Colne Valley site – one based on a high court order obtained on 28 November granting it possession of a particular part of the site, and the second based on the HS2 act passed by parliament, which officials say gives them the right to obtain possession of the land from which they are evicting protesters.

The site is in the Ruislip, Northwood and Pinner constituency of the Conservative MP David Simmonds. The constituencies of John McDonnell and Boris Johnson are in the same borough. There are five anti-HS2 protest camps along the rail route. Protesters fear that if the Colne Valley camp is demolished the others will follow.

Speaking at the site, Sarah Green, 63, said: “This eviction is totally undermining our right to protest and freedom of assembly which has been granted to us by the high court. People are being made homeless without being given the opportunity to go to court to contest this eviction.”

Green and a second protester, Laura Hughes, walked free from court last July after a prosecution against them collapsed. Both had been charged with aggravated trespass for protesting against HS2 work on the Colne Valley site.

A district judge, Deborah Wright, dismissed the case after she said it was not possible to prove beyond reasonable doubt that the protesters were trespassing on land in the possession of HS2.

Protesters involved in the eviction are questioning which parts of the site HS2 has possession of. HS2 had previously admitted that a map it provided to the Crown Prosecution Service outlining which part of the site was covered by a high court injunction against protesters was incorrectly labelled.

Various maps of land held by HS2 and the boundary of the high court injunction were submitted as part of the prosecution case. However, there has been confusion about exactly what land was owned by HS2.

A high court ruling last November granted HS2 possession of part of a footpath on the Colne Valley site but did not specifically authorise it to gain possession of the area where the protest camp is sited.

A Hillingdon council spokeswoman said: “HS2 Ltd has used the HS2 Act to compulsorily acquire and take possession of several parcels of land west of Harvil Road, from the council. This was not a voluntary sale.”

A spokesman for HS2 said: “This is land that is legally possessed by HS2. Protests such as this are costly to the taxpayer and are a threat to the security and safety of the public and our workers.

“We understand people feel strongly about the project and that they want us to hear their views, which is why we have numerous channels through which they can make their feelings understood. Investment in a state-of-the-art, high-speed line is critical for the UK’s low-carbon transport future, will provide much-needed rail capacity up and down the country, and is integral to rail projects in the north and Midlands which will help rebalance the UK economy.”