London commuters are in for a miserable time on what is likely to be the hottest day of the year.

As well as sweaty smelly conditions in sweltering crowded carriages, train passengers can also look forward to delays caused by the weather.

Temperatures of 29.1C (84F) were recorded at Heathrow Airport yesterday afternoon, and the heat caused problems for rail services.

Train companies had to cancel journeys or slow them down after Network Rail warned tracks could buckle in the heat.

Some fast trains from Paddington were cancelled, with other services curtailed.

Thameslink and Southern passengers were also affected by restrictions.

Expect train delays, consider avoiding travel

Network Rail is warning there could be a similar situation today and that all train passengers can expect delays as the mercury is set to rise further.

Temperatures are predicted to hit 35C (95F) today.

A Network Rail spokeswoman said: "There are speed restrictions all over the country due to the hot weather so there will be some delays and some disruption.

"We apologise to passengers for delays but obviously the restrictions are in place to minimise disruption on the network."

Train operator Southeastern said Network Rail had advised it would be imposing speed restrictions across many parts of its network during this afternoon and evening.

It said in a statement: "This is likely to cause disruption to trains although we will be aiming to run all services.

People might wish to avoid travelling between 1pm and 7pm, it added.

Unfortunately other travel options are no more attractive than the disrupted trains, with complaints aplenty on social media about unbearable heat on London buses.

Firms urged to let staff travel outside rush hour

Employers have been urged to be flexible and allow staff to travel outside rush hour to avoid overcrowded public transport.

Dr Angie Bone, head of extreme events at Public Health England (PHE), said: "During very hot weather, pregnant women and people who have chronic illnesses, including cardiovascular, respiratory, renal conditions, diabetes or Parkinson's disease, may experience discomfort if indoor temperatures are particularly hot and in using public transport.

"Employers should ensure indoor areas are kept cool and consider allowing these individuals to travel to or from their place of work during cooler, or less busy times of the day. For those working or exercising outdoors, strenuous physical exertion during the hottest part of the day should be kept to a minimum."

A level 3 heatwave alert - one below a national emergency - could be issued.

When the alert is triggered, social and healthcare services must mobilise community and voluntary support for high-risk groups and media alerts about keeping cool are issued.