LONDON SIZZLES

HEATWAVE BUILDS AS UK TEMPERATURE RECORD 'SET TO FALL'. COMMUTERS' MISERY ON SWELTERING JOURNEY TO WORK. SOME SCHOOLS CLOSE AND NHS BRACES FOR INFLUX OF PATIENTS

- Ross Lydall and Rachael Burford

LONDON today baked in a potentially record-breaking heatwave as "really ferocious" temperatures took their toll on the transport network, offices, schools and hospitals.

About half of Tube lines were shut or suffering severe restrictions, rail companies advised against travel and the London Ambulance Service (LAS) pleaded with Londoners to only call 999 in a "genuine emergency".

With the capital hotter than the Western Sahara and amid predictions of a 40C hottest day in the UK, many followed advice to stay in the shade and work from home.

In key developments:

 Some schools rejected government advice to remain open and told pupils to stay at home.

The LAS said it expected to receive up to 8,000 emergency calls today, 2,500 more than a "normal" busy day.

Health chiefs said they would do all they could to avoid patients getting stuck in ambulances outside hospitals.

Tube bosses shut the Hammersmith and City line as the Jubilee, Central and District lines suffered "severe delays".

Londoners faced a sleepless night with temperatures staying above 23C.

Police searching for a missing 13-year-old who got into trouble in a river near Ovingham, Northumberland, found a body

Chief executive of the Met Office Professor Penelope Endersby said while today "may well see the hottest day in the UK in history", tomorrow could be even hotter, with some forecasts estimating highs of 43C (109F).

Forecasters said temperatures would ease from Wednesday but admitted heatwaves could become a "regular occurrence".

Cabinet Office minister Kit Malthouse said the UK had a "difficult 48 hours coming", with the record 38.7C temperature recorded in Cambridge three years ago almost certain to be broken. Mr Malthouse, who was due to chair a third Cobra emergency committee this afternoon, was challenged when he claimed the country was "quite well prepared".