Costain, Murphy and Morgan Est bid to build £430m tunnel under north London

A trio of contractors have returned bids for a £430m tunnel underneath north London.

Costain, Murphy and Morgan Est have sent in bids to client National Grid to build a 27.5km tunnel from Hackney in east London to Willesden Green in the west of the capital.

The project for National Grid comprises a four-metre diameter, 27.5km-long tunnel, which will be built in two sections. The largest section will comprise a continuous stretch measuring 20km.

A decision is imminent, with a start on site pencilled in for late November and work is expected to be completed by around 2015.

The proposal is part of National Grid's £15bn programme of capital works with the utility expecting to invest around £3bn a year until 2012.