Trains on some of the country's busiest routes were cancelled or delayed yesterday evening because of emergency engineering work and signalling problems, causing travel chaos for thousands of passengers.
St John Ambulance teams in London have treated record numbers of people for heat related conditions at Wimbledon, Hampton Court and the Hyde Park Barclaycard British Summer Time concerts, the service said today.
Volunteers assisted over 3,000 people in the past three weeks as temperatures soared and people wilted under the onslaught of heat, dehydration and breathing difficulties related to high pollen counts.
Transport union RMT has criticised government cuts to services after rail and tube commuters suffered rush-hour delays again today on another hot warning.
RMT general secretary Bob Crow said: "We have warned that cuts to maintenance and under-investment on Tube and rail would lead to a spate of breakdowns in extreme weather and those warnings have been borne out with a vengeance last night and this morning."
Rail and Tube travellers have suffered rush-hour delays on another scorchingly hot morning. There were hold-ups on three London Underground lines, while the imposition of a speed restriction affected Greater Anglia main line trains running into the capital.
On the Tube, emergency engineering work at Finsbury Park in north London meant the Victoria line was part suspended for a time, with delays continuing into the heart of the rush-hour.
Signal problems also led to delays on the District line and on the Northern line.
South West Trains has apologised after trains on some of the country's busiest routes were cancelled or delayed yesterday evening because of emergency engineering work and signalling problems.
Services to and from London Waterloo were hit at the height of the evening rush hour.
A spokesman said today:
At 14:00 a two inch kink in the rail was identified outside Waterloo station which meant we had to close four platforms at the station and as such, lost a vital section of track which allows us to run our advertised service.
Train services to and from London Waterloo were heavily delayed for the remainder of the day and many were overcrowded as a result. The decision to run an alternative service plan was not taken lightly and when such a decision is taken we consider the safest and most efficient way of running our network to get everyone home as quickly as possible.
Due to the nature of yesterday's incident and the critical location where it occurred, this unfortunately meant that many customers were heavily delayed on their journey home.
We do everything possible to prevent the kind of disruption you experienced yesterday. I would also like to assure you that we are working hard to replace ageing parts of the rail system to deliver a better, more reliable service.
"We would like to apologise for the disruption our customers will face on their journeys home tonight.
As a result of emergency engineering work to fix a track defect, we are unable to use four platforms at Waterloo which is having a serious impact on the services we can deliver.
Because of that we will have to run an amended timetable for the rest of the day.
Safety is our absolute priority. We have no choice but to make sure these repairs are carried out before we can restore train services. We expect to run a normal service from tomorrow morning. We would like to apologise again to our customers for this and thank them for their patience"