“When the air temperature reaches 30 degrees, the temperature on the rail can actually be up to 20 degrees higher.”
British rail is stressed for 27 degrees, the average summer rail temperature. Hit 30 in the air and the steel can be 20 degrees hotter, so trains crawl or stop. Slab track would fix it and costs four times as much. Britain built for the climate it used to have and is now paying for it in delays.