Workers digging tunnels for HS2 at Euston have secured union access following a five-year campaign.
Unite has secured an access agreement to ensure workers on the project can seek advice and support from a union official while on site.
An agreement has been signed between the union and the joint venture company Skanska, Costain, Strabag (SCS), which is building the tunnels that will carry HS2 trains in and out of central London.
A union officer will be able to meet with workers in the site's rest areas during breaks and the union will also be able to attend induction meetings to talk to workers.
The agreement means all major parts of the HS2 development are covered by union access agreements.
Unite general secretary Sharon Graham said: “The persistence and dedication of Unite construction members should be congratulated; it is their hard work which has ensued this access agreement has been signed.
“Construction workers based on the SCS project will now be able to freely consult a Unite official about all their employment and safety concerns.
“The signing of this agreement will ensure that Unite is now fully able to defend and enhance workers’ jobs, pay and conditions at HS2.”
Unite regional co-ordinating officer Vince Passfield added: “This has been a long and challenging campaign to secure standard union access to this site.
“Now that it has been achieved Unite will ensure that workers will have their employment concerns swiftly and properly dealt with.”