Summer sunshine became the latest meteorological phenomenon to paralyse Britain's railways yesterday, proving as disruptive as the wrong kind of snow, leaves on the line, unexpected condensation and high winds.
Network Rail imposed speed restrictions of 60mph across much of southern England and the Midlands, on the grounds that high temperatures could cause rails to buckle. The move, which is likely to stay in force all week, increased journey times from London to Manchester by up to an hour.
Virgin Trains announced it was halving the number of services between London and Birmingham to one an hour, to avoid a slow-speed logjam. Most trains leaving Birmingham New Street were affected by the speed restrictions, with Virgin passengers facing average delays of up to an hour.
Central Trains advised passengers travelling from Liverpool to Stansted airport to allow up to six hours for their journey. A spokesman said services between Rugeley Trent Valley and Stafford had been replaced with buses. Some services between Birmingham Snow Hill and Dorridge, near Solihull were also cancelled.
Network Rail's engineering director, Peter Henderson. said the restrictions were "necessary and sensible" with temperatures expected at more than 30C. Many speed restrictions will operate between lunchtime and early evening, the hottest period of the day.
A source at one train company said Network Rail lacked records going back to 1990, which was the last time temperatures hit the high 90s forecast for the rest of the week. "They're being extremely cautious," said the source. "They're not convinced they've got enough information to know what will happen to the track."
Roger Ford, technical editor of Modern Railways, said steel was typically set at a "neutral" temperature suitable to the local climate, with leeway to allow it to expand in the heat or shrink in cold weather.
Unusual summer peaks can cause the track to become too large for its fastenings, causing the metal to fracture. Network Rail insisted the problem was "not unique to the UK". However, a spokesman for Deutsche Bahn said the only summer problem for Germany's railways was that on-board air conditioning sometimes struggled to cope.
In France, a spokesman for the state-owned SNCF said: "We slow down trains when there's been an accident but never because of the temperature." He pointed out that trains between Paris and Marseille were running at 215mph yesterday, despite temperatures as high as 34C (93F).