Rail passengers were gasping for air this morning on trains at the beginning of the expected hottest day of the year.

South West Trains said it did not expect delays due to the heat - expected to reach 34C (93F) in London.

Reports yesterday said train companies were forced to cancel journeys or slow them down after Network Rail warned tracks could buckle in the heat. Steel rails can warp as they reach 20 degrees centigrade above air temperature.

Network Rail is expected to impose speed restrictions on parts of the Southeastern network this afternoon and evening, due to the heat. Southeastern says the changes are expected to cause disruption and warned travellers to carry a bottle of water.

Passengers were crying out for some air conditioning on their trains. Their plight was made worse by reduced carriages on some trains.

warm conditions at Wimbledon forced officials to reduce capacity to allow fans to cope.

The mercury hit 29.3C (84.7F) in SW19, as it did commonly around the country, and a Wimbledon spokesman said: "We have reduced today's initial capacity slightly to 38,000 to allow people more room in the grounds and therefore more space in the shade and easier access to the free water points.

"The daily capacity is dependant on the number of courts in operation and the prevailing weather conditions so it would not be the first time we have regularly adjusted the daily capacity."

Yesterday's highest mainland reading of 30.5C was at Northolt, west London, while a reading of 33C in Jersey was in St Helier.

The highest recorded July temperature was at Wisley, Surrey, in 2006, where the mercury peaked at 36.5C (98F).

How are you coping with the heat? Let us know at digitalmedia@london.newsquest.co.uk

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