Passengers travelling to London from Cornwall by train have been warned to expect “significant changes” between Christmas and the New Year – and booking will be essential.

GWR said that while there are no major planned alterations before Christmas Day, between December 27 and December 29 there will changes to both the end location and how passengers can travel.

After Christmas Eve no main line trains will run to or from London Paddington until Monday, December 30. This is to allow for work on the new HS2 station at Old Oak Common in west London, and Network Rail improvements to track, signals and overhead wires between Reading and Paddington. 

Most of Great Western Railway’s long-distance services will start from or terminate at Reading, where customers will be able to pick up connecting trains to Ealing Broadway from where London Underground services run into central London. 

However, trains travelling from Cornwall and Devon, or from South Wales, after Christmas will have an hourly service that will end at London Euston instead – and these trains will not stop at Reading.

The company said that to help keep customers comfortable and minimise crowding, these trains would be by reservation only, making it essential for passengers to book beforehand.

GWR operations director Richard Rowland said: “This is a really complex operation, and we have worked hard to make sure people get to where they want to. 

"We will run an hourly service from the south-west of England – Cornwall, Devon – and an hourly service from South Wales which will go into Euston. 

“We will then have several trains which will terminate at Reading, and people can connect there, and we will also have trains to Ealing Broadway for those making more local journeys. They will be able to connect there on to the London Underground and into London that way. 

"It is really important to us that we can keep customers moving and get them to where they need to go this Christmas. One of the reasons we chose Euston was that its most convenient for many of our customers who are making journeys beyond West London.

"We’ve worked carefully with the team at Network Rail who manage that station to make sure we've got extra staff and managers to help customers. We will be transporting a little bit of Great Western Railway to Euston to keep people moving." 

Those travelling are, however, warned that trains and stations over the Christmas period are expected to be extremely busy – and that the earlier you can travel before Christmas, or the later you can travel after it, the more comfortable your journey will be.

 Network Rail western route director Marcus Jones said: “Our festive upgrades ensure the railway runs reliably and safely. 

"Continued investment into upgrading and improving the railway is evidence of our commitment to providing a railway fit for the 21st century. 

"We appreciate there is never a good time to disrupt journeys but whenever possible we do this at times when fewer people are travelling, such as at Christmas, on bank holidays or at weekends.  

"We thank passengers in advance for their patience and urge them to please check before they travel.”  

Passengers are advised to check their journeys before travelling and to plan well in advance. More information can be found at www.GWR.com/Christmas