The contract, which will be formally signed shortly, is expected to be worth in the region of £300m to the joint venture, with optional contract extensions.

There is also a separate maintenance contract following the design and build phase that will operate for seven years worth around £32m for the joint venture. 

Costain has enjoyed a successful month of work winning on HS2 after also clinching a £400m sole supplier deal to deliver tunnel and lineside mechanical and electrical systems.

Work on the first elements of the M&E deal will start in the first quarter of 2025 and run for a seven-year period, with the option for additional contract extensions.

Alex Vaughan, CEO of Costain, said: “This contract marks the start of a new partnership with Siemens Mobility and its team of experts who share our values and ambitions.

“Providing a safe, reliable power system will be critical to the success of HS2, with rail electrification a crucial part of the UK’s decarbonisation plans.”