The agreement secures the right of Unite officials to visit the project’s inductions and rest facilities to talk to all the workers on the site during their breaks, in order to deal with any concerns or worries they may have.

The access deal was signed after a two-year campaign by Unite, which included regular demonstrations, leafletting workers and resolving their concerns.

It leaves London tunnels consortium Skanska, Costain, Strabag as the last remaining main works contractors denying unions access to their sites with all other JVs – BBVS, Align, EKFB and  Mace/Dragados – now holding agreements.

Unite regional officer Declan Murphy said: “Agreeing trade union site access should be a matter of course for all construction contractors.

“But the successful campaign to achieve the agreement with BBVS shows that Unite will overcome any obstacle put in its way to ensure workers are not denied union access. Unite will now be turning its complete attention to securing a site access agreement for SCS workers.”