A team from SCS will construct a 4.5-mile twin-bore tunnel between Old Oak Common and Euston using two tunnel boring machines (TBMs), named Karen and Madeleine.
The first TBM, Madeleine, is scheduled to be launched on the up line next week, with the second machine, Karen, expected to follow approximately a month later on the down line.
Once fully operational, the TBMs are forecast to progress at speeds of up to 150 metres per week, working at depths reaching around 50 metres.
Both machines are programmed to arrive beneath the Euston approaches by June 2027.
Following completion of the main tunnel drives, the TBMs will be dismantled within an underground cavern beneath Parkway Junction and removed in sections by road.
While funding is currently secured to complete the tunnels up to just short of Euston, the final design and funding approval for the sections extending into a rebuilt Euston station are yet to be confirmed.
These remaining sections will be excavated by hand using sprayed concrete lining. Under the proposed design, one tunnel will divide into two, forming a three-tunnel arrangement.
This configuration will deliver two tunnels for arriving services and one for departures, providing greater operational flexibility for routing trains into the Euston platforms.