Britain's railways are wilting in the latest heatwave, with operators worried the rails might buckle in the high temperatures.
Commuters are used to hearing about leaves on the tracks, flooding and even the wrong type of snow. But this time it's the heat that is causing chaos.
Speed limits on some of the busiest routes across the network have been lowered, causing delays for thousands of travellers.
Long-distance Virgin services will be worst hit with extended journey times between London and Birmingham, Manchester, Crewe and Scotland.
Peter Rayner, an expert in railway operations and safety, said: "They are saying there is a chance of a buckled rail so we will impose speed restrictions, which is commendable.
"What does need to be answered, however, is how the railway network has been able to get into the condition where such action is necessary.
"That brings us back to the stewardship of Railtrack and probably their contractors who have, over the years, failed to put sufficient ballast down, which is an intrinsic part of this problem."
Forecasters believe this could be the hottest week of the year - and possible they hottest week ever.
Among other services affected are those between London and Birmingham - reduced from half hourly to hourly - and the West Coast main line between Euston and Crewe has a 60mph limit.
A 60mph restriction has also been imposed across southern England until early evening.
Routes from London's Liverpool Street to Chelmsford and Norwich will also be affected.
Sky News weather presenter Lisa Burke says there will be "copious amounts of sunshine" just about everywhere with temperatures rising through the week as the hot air drifts up from the continent.
"It's going to be hot, 35C in the South," Lisa said.
"We might even see the record broken in the south-east."
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