Commuters are urged to check their journeys before they travel as RMT rail workers take industrial action.

The latest strike action, in an ongoing dispute over pay, will see services start later and finish much earlier than normal.

Most services are expected to run between 7am and 7pm, but some stations - namely Plumpton and Cooksbridge, will be closed due to the walkout.

Trains that do operate are expected to be very busy, with some passengers not able to board their usual train.

Strike action will also take place on Saturday, July 22 and next week.

Chris Fowler, head of network operations for Govia Thameslink Railway - which runs Southern, Thameslink and Gatwick Express services, said: “We are really sorry about the impact that this round of industrial action will have on our customers, especially as many will be looking to start their summer holidays.

“Where possible, we’re running as many trains as we can, but unfortunately there will be some days and times when people will be left without a service.

“It’s incredibly important that people check every journey they plan to make before they travel and leave plenty of time, as our services will be much busier during this period.”

The first train services today will leave Brighton significantly later than normal. The first service to London Bridge will depart at 7.16am, with the first train to London Victoria leaving at 7.29am. The first train to Hove won't leave until 7.58am.

The last service from Hove to Brighton will leave much earlier than usual at 6.35pm, with services from London Bridge and London Victoria departing for Brighton at 8.35pm and 8.50pm respectively.

Due to the disruption, non-stop Gatwick Express services between London Victoria, Gatwick Airport and Brighton will not operate.

Extra stops at Clapham Junction and East Croydon have been added to Southern services to and from the airport to help customers.

Gatwick Express tickets are being accepted on Southern and Thameslink services at no additional cost.

RMT general secretary Mick Lynch said the strike action would show the country “just how important railway staff are to the running of the rail industry”.

He said: “My team of negotiators and I are available 24/7 for talks with the train operating companies and government.

“Yet quite incredibly neither party has made any attempt whatsoever to arrange any meetings or put forward a decent offer that can help us reach a negotiated solution.

“The government continues to shackle the companies and will not allow them to put forward a package that can settle this dispute.”