Passengers on one of the country's busiest rail networks will need to plan their journeys as a new timetable is introduced.

Govia Thameslink Railway (GTR) has promised a "package of changes" to help make journeys easier for commuters, however has warned some "may be disappointed" with the alterations.

From Sunday, May 21, train times will be changed nationally with GTR, which operates Southern, Gatwick Express and Thameslink, saying the improvements will "better reflect demand".

The company said the new timetable will be easier to plan around as trains are set to arrive and depart at regular intervals across the South East. 

The Argus: A class 313 trainA class 313 train (Image: The Argus)

The change has been months in the planning, with Phil Hutchinson, head of strategic planning at GTR, leading the team behind the timetable improvements.

Services along the coast will be changed to coincide with the removal of the 47-year-old Class 313 trains, which are to be replaced with more modern Class 377 units.

Phil said: "This isn't just a timetable change, but more a package of changes which align with the removal of the 313s.

"We've had to completely change the way that we think about timetable planning since covid.

"We have been looking intrinsically at our demand to unlock improvements to the service without increasing the overall cost to the taxpayer."

The biggest changes with the new timetable will be along the East Coastway route, between Brighton and Ashford.

A new service from Brighton to Eastbourne will run off-peak, which together with connections between trains, is designed to offer more options for journeys between Brighton, Eastbourne and Hastings.

But the regular Brighton to Lewes service is being axed with services travelling a longer distance taking its place. 

Phil said: "In the peak hours, we would run five trains per hour between Brighton and Lewes, and three per hour off peak - and one of these was the shuttle. However, we have found this was not well utilised.

"So instead, there will now be a consistent four trains per hour, all day to Eastbourne."

The twice-hourly service between Brighton and West Worthing will also be doubled, to match that of the Lewes services - with the Hove shuttle service extended to West Worthing.

The Argus: Norman's Bay station with a class 377 departingNorman's Bay station with a class 377 departing (Image: Wikimedia Commons)

Some of these changes have been possible due to reallocating fleet across the network, as the Class 313 trains are replaced with more modern class 377 and 387s.

This means some services could see less carriages, which in turn creates more services elsewhere on the network.

Phil said he hopes the changes "make a significant improvement" to the areas the railway serves.

Coastal hamlet Normans Bay, on the same line, will be disconnected from Ashford as the Eastbourne service no longer stops there, replaced by the London Victoria to Ore train.

Thameslink's Littlehampton to London Bridge service, operated by Thameslink, has shifted to a Southern train and will no longer call at Gatwick.

A spokesman for GTR said the timetable changes, alongside more modern trains "will help deliver an improved service, delivered with the input of rail user groups to help make services better for passengers, especially during the summer holidays".