'Do not travel': LNER says NO TRAINS will run between Leeds and London on Tuesday

“On Tuesday July 19, DO NOT TRAVEL between #LondonKingsCross and south of #York & #Leeds, as no trains will run,” it said in a tweet. “Only travel if necessary to other destinations.”

People who have already bought tickets are urged to visit the LNER website for information about refunds.

Elsewhere train operator Northern is calling on its customers only to travel on Monday and Tuesday if it is essential with 'significant disruption' expected.

A statement on its website reads: "During high temperatures, trains will need to run slower due to speed restrictions being put in place which will extend journey times significantly. We are also looking to reduce the number of trains running on the network meaning there will be some short notice changes in advance of and on the day of travel, additionally we are expecting disruption to the limited number of services running.

"You should only attempt to travel if absolutely essential and check regularly before travelling. Online journey planners will be updated as soon as possible but some changes may not show until the day of travel so we advise to keep checking back."

It says fee-free refunds will be available for standard anytime, off-peak and advance tickets if customers decide not to travel.

"If you travel and your train is delayed by 15 minutes or more then you will be entitled to delay repay compensation. Season ticket holders can also claim compensation, if not travelling, through delay repay."

Northern has also issued tips for travelling in the heat. They are:

*Carry a bottle of water with you to keep hydrated

* If waiting at a station, try and find a safe spot in the shade

* If you do have to go into the sun, apply some sun cream and wear a hat

* If you start to feel ill; do not board the train, speak to a member of staff or use the help point at the station

Rail passengers can find out how high temperatures can impact the railway by visiting the Network Rail website.