Bouygues Murphy JV has entered talks to buy a monster TBM to drive one of the widest tunnels in the world for the Lower Thames Crossing.

The JV will use just one machine to drive both 16.4m wide north and southbound tunnels, keeping costs down while not impacting the total programme schedule.

Tunnelling machine procurement gets underway as it emerged the mega project cost is heading towards £11bn, up from the £9bn cited earlier this year. The Government is due to foot £3.1bn of the cost, leveraging £7.5bn of private funding for the project.

Digging of the first of the three-lane 4km long tunnels will begin in 2028.

Next summer, construction will begin on the northern tunnel entrance, a 26m deep launch chamber that will also host a temporary segment factory producing the concrete rings for the tunnel lining.

Working at a maximum of 65m below the surface of the Thames Estuary water pressure could reach 6.5Bar so the TBM will be designed to safely contain this pressure.

Once complete, the entire structure will be buried under Tilbury Fields, a new landscaped park overlooking the Thames near the docks.

Roads and Buses Minister Simon Lightwood said: “The launch of the procurement process for one of Europe’s largest tunnelling machines marks a major step forward for this transformational project, backed by £891 million in the Budget which demonstrates this Government’s determination to deliver the infrastructure our economy needs to grow.

“By unlocking vital capacity across the Thames, the Lower Thames Crossing will relieve congestion at Dartford and create better connections between our ports, manufacturing centres and communities, but also be a key driver of jobs, growth and opportunity.”