Preparations for the £2.8bn electrification of the South Wales mainline to London are starting soon, but will cause delays – but it will be worth it for everyone in the end.

Rail travellers face six weeks of disruption as works starts to prepare to electrify the Severn Tunnel. Network Rail said it will shut the tunnel for nearly six weeks from September. It will be the longest closure of the 130-year-old tunnel for at least 50 years. Passengers will be diverted via Gloucester or use replacement buses, adding at least an hour to journey times.

The work is to prepare for the £2.8bn electrification of the South Wales mainline to London. The actual electrification of the section from Bristol to Cardiff is not expected to be completed until December 2018, according to the latest timetable published by Network Rail. 

Work has already been carried out with four tonnes of soot removed from the tunnel walls and 7,000 holes drilled into the roof. A conductor rail will be installed to provide power. Network Rail said there would be fewer services while the tunnel is closed and added that the work would take four years if only done at weekends.

David Sidebottom, from the group Passenger Director for Transport Focus which represents rail users, said: “The important thing is actually hearing from passengers, and this is the beauty of social media these days. We’ll be gathering that up and making sure Network Rail and train companies are listening to the experience on the day because there will be times when they don’t get things right and it’s important they learn from that and put it right for the following day.”

Dan Tipper from Network Rail said: “We have a significant volume of work going on across the western and Wales routes, and we have to avoid disrupting passengers twice in one journey, so we have to pick a time when we avoid other works.”

Electrification is expected to cut journey times between Swansea and London by 20 minutes. The tunnel will shut on 12th September and reopen on 21st October.