Severn Tunnel electrification upgrade a 'mammoth task'
A six-week closure to upgrade the Severn Tunnel for electric trains to use in and out of Wales is costing £10m, Network Rail has said.
It is shut until 21 October so the work, which is part of the wider £2.8bn scheme to electrify the main line from London to south Wales, can take place.
Three teams of 200 engineers are working 24 hours a day for six weeks.
Their work has included installing a state-of-the-art power rail in the tunnel roof.
Tim Butler, of Network Rail, said fitting five years' of work into six weeks was a "mammoth task".
Jordan Davies reports.
05 Oct 2016