The Northern Line Extension requires 3,280 no. 5.2m-diameter rings for 2.4km of twin tunnel. Ridham can produce 70 rings per week according to Morgan Sindall, with 45 people working over two shifts.

David Hicks, Morgan Sindall’s senior operations manager at the Ridham facility, said: "It’s great to be remobilising the facility and recreating opportunities for the local community. We’re currently re-commissioning the factory, getting it ready for production ahead of the start-up date in July. We’re pleased that our capabilities here will help with the completion of key infrastructure upgrades in London".

The last major order was for the Lee Tunnel project, which runs for 7.8km and required 7.8m-diameter rings.