Record-breaking temperatures last week severely disrupt trains between St Albans and London

Trains between St Albans and London were cancelled during last week's heatwave. Picture: Peter Alvey

Trains between St Albans and London were cancelled during last week's heatwave. Picture: Peter Alvey - Credit: Archant

Govia Thameslink train services into London from St Albans were seriously affected by high temperatures last week.

Thursday, July 25 was the hottest July day on record in the UK, with temperatures soaring to 38°C in Hertfordshire.

The scorching temperatures forced Thameslink to place a speed restriction during the day, and then overhead wire damage led to all trains being cancelled between St Albans and St Pancras.

A Govia Thameslink Railway (GTR) spokesman said: "For safety reasons, due to the risk of rails buckling in the record-breaking temperatures forecast on Thursday, Network Rail placed a 60mph speed restriction across our network from 12 noon that day.

"Normally, our trains can travel at up to 100mph on much of the route between London and Bedford.

"We were able to run our normal peak services on Thameslink in the morning, however, with the prospect of trains running more slowly from 12 noon we began to introduce, from 10am that day, an amended timetable with fewer services between London and Bedford in both directions.

"There was no alternative because the speed restrictions meant trains were taking longer to make their journey.

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"Some trains ran non-stop between stations to reduce the overall delay into London. As a result of this, passengers travelling between Bedford and Luton or Harpenden were advised they would need to change trains at Luton or St Albans to reach their destination.

"Passengers were advised to board the first available service towards their destination, changing en route."

With the services already reduced by speed restrictions, trains were further affected by unprecedented damage to the wires.

The spokesman said: "The amended timetable was running well until, on Thursday afternoon, overhead wire damage in Belsize Tunnel near West Hampstead, and an associated lineside fire, blocked the entire rail route.

"There was further disruption on other routes making those trains that were running extremely busy.

"More overhead lines came down at Peterborough and between Kings Lynn and Cambridge on Thursday.

"This put trains out of position disrupting the following days service as well. Engineering work also overran on Sunday morning between Cambridge and Royston."

As of Monday night, GTR was still running a reduced timetable with 11 trains per hour instead of the usual 16.

Thameslink journeys continued to be disrupted due to the damages to the overhead wires at West Hampstead, with a heavily reduced service for all stations between St Albans and St Pancras.

People have been advised to travel earlier than they originally intended to ensure they arrive at their destination on time. Ticket restrictions have also been withdrawn, meaning customers with off-peak tickets can travel at any time of day.

GTR also explained why East Midlands trains were able to run a full service on Monday despite the damage to the wires.

A spokesman said: "East Midlands Trains operate using a different type of train. Thameslink trains in this area are operated by drawing electricity from the overhead lines, whereas East Midlands Trains' services are all operated with diesel trains and don't require the use of overhead lines at any point during their journeys.

"The overhead lines above one of the pairs of tracks through the West Hampstead area are currently unserviceable.

"This limits Thameslink to one line in each direction between Kentish Town and Radlett.

"In turn, this means a reduced service will be in place before Network Rail fully complete repairs."

Despite commuters on Twitter reporting issues with the air conditioning on trains, GTR said the majority of trains have functional air conditioning and station staff hand out water on platforms in hot weather.

Network Rail's website explains that train tracks can become as much as 20°C hotter than the air temperature in warm weather.

Most of the network can operate when track temperatures reach 46°C, but temperatures have previously been recorded at 51°C. As tracks are made of steel, they expand when they get hotter and can start to curve, which is known as 'buckling'.

Local speed restrictions are introduced when remote monitoring systems tell Network Rail a section of track may be expanding too much.