Rail passengers travelling from South and West Wales towards London face longer journeys for much of the summer, as a month of engineering works gets under way next week.
From Monday 6 July to Sunday 2 August — and again on the weekend of 8 and 9 August — trains between London Paddington and South Wales will be diverted, adding around 25 minutes to journey times.
Services will also run less often, with trains once an hour rather than more frequently while the work takes place.
The disruption affects anyone travelling the main line towards London from stations including Swansea, Neath, Port Talbot, Llanelli and Cardiff.
Great Western Railway and Network Rail say the works, between Swindon and Bristol Parkway, are needed to improve the long-term reliability of the route.
Network Rail will replace track and carry out structural work in Chipping Sodbury tunnel, alongside track renewals west of Swindon.
The companies say the investment will deliver a more resilient railway and help protect services against extreme weather in the future.
It follows a £23m upgrade to the overhead lines inside the Severn Tunnel, which Network Rail completed in early June after 16 days of works on the cross-border route.
No rail replacement buses are planned, and trains will continue to run throughout the works.
Some services will have altered stopping patterns to help keep trains moving along the route, GWR said.
To ease the disruption, extra trains will run between London Paddington and Swindon, giving passengers more options on that stretch.
GWR’s station manager for Swindon and Bristol Parkway, Marcus Deegan, said the work was an important investment in the route’s future.
“We know longer, less frequent journeys are an inconvenience in the short term, so we’re doing everything we can to help,” he said, urging passengers to plan ahead and check before they travel.
Michael Pinkerton, a portfolio manager at Network Rail, said teams would be working “day and night throughout the summer” to deliver the upgrades as efficiently as possible.
He said the work would make the railway more reliable for passengers “long into the future” while strengthening the route against extreme weather.
Passengers are being urged to allow extra time, especially for connections, and to reserve seats in advance where available. Free seat reservations are available.
GWR is encouraging travellers to check before they set off at gwr.com/upgrade and to sign up for journey alerts for real-time updates during the works.
