Milton Keynes commuters warned heatwave could cause delays on the trains by buckling tracks

When steel becomes very hot it expands and rails can bend, flex and, in serious cases, buckle, say Network Rail .

As a precaution, trains have to run at slower speeds.

With UK heat record expected to be broken tomorrow, railway staff are today preparing for this challenge.

James Dean, chief operating officer for North West and Central, said: “Keeping passengers moving is always our top priority. But we want people to be prepared. If the soaring temperatures do lead to us having to put in place slower speeds for safety reasons, please bear with us our engineers work to fix the problem. It may mean some journeys take longer."

He added: “For those who must travel by rail, we’d remind people to carry some water with them so they don’t get too parched, and always check before travelling so they know exactly what to expect.”

For more information on how Network Rail deals with the hot weather visit the website.