Train services including ones between Carmarthen and Pembroke Dock will be affected by track replacement work in the Severn Tunnel and essential maintenance in the Patchway area during July.

The planned engineering works will impact trains between Bristol and South Wales from Wednesday, July 3 to Thursday, July 18, with further work on the weekend of July 27-28.

• Trains between London Paddington and Swansea, Carmarthen or Pembroke Dock will run but will divert via Gloucester – not stopping at Bristol Parkway

• A limited train service will run between London Paddington and Bristol Parkway – otherwise travel via Bristol Temple Meads instead

• Trains will run between Portsmouth Harbour and Bristol Parkway

• Trains also run between Penzance, Plymouth or Taunton and Bristol Temple Meads

• Trains will still run between Bristol Temple Meads and Gloucester or Cheltenham Spa, where trains will be running to/from South Wales

• Limited replacement buses are planned between Bristol Parkway and Severn Tunnel Junction (Mon-Sat), or Newport (Sun only)

• Valid rail tickets will also be accepted on the M4 bus service between Bristol Parkway and Patchway stations

Unlike previous Severn Tunnel blockades, there will not be a full rail replacement service – customers can travel by train and change at Gloucester instead.

Further engineering work will also take place on the weekend of August 24/25 impacting train services that normally run between Bristol and South Wales.

For the latest information, visit GWR.com/SevernTunnel.

Nick Millington, Network Rail Wales and Borders route director, said: “We recognise there is never a good time to close the Severn Tunnel, but we have planned this essential work to minimise disruption as much as possible.

“Our dedicated teams will be working 24/7 in challenging conditions to deliver the largest track replacement in the tunnel for many years, which is vital for the continued safe and reliable running of train services along this busy route.

“We would like to thank passengers for their patience – and urge them to check their journeys before they travel.”

Marcus Deegan, GWR Station Manager for Bristol Parkway and Swindon, said: “This rail improvement work forms part of an important programme of maintenance to help ensure we can continue to provide customers with consistent and reliable services.

“To maintain rail connections to and from South Wales, some of our trains will use a different route from normal, via Gloucester, making journeys slightly longer.

“We can only provide a limited replacement bus service between Bristol Parkway and Severn Tunnel Junction in the morning and the evening Monday to Saturday.

“So instead, we’re asking customers in the Bristol area to stay on the train and to change at Gloucester for train services to South Wales, and vice versa.

“There will be a full rail replacement service on Sundays between Bristol Parkway and Newport as fewer trains will run between Bristol and Gloucester.”

A number of major events including concerts are scheduled to take place in Cardiff city centre, plus Chepstow Racecourse, so please check carefully before you travel.