Train is derailed as torrential floods hit the south

At around 7am the 6.19 London Midland service from Milton Keynes to London Euston “remained upright” after a small section of the train left the track - there were no reports of any injuries, despite a train heading north giving the derailed service a “glancing blow”, Network Rail said.

Initially, all four lines of the West Cost main line were closed at the scene, but two were reopened at around 8am.

The incident caused major delays to services and London Midland warned passengers to avoid travelling to or from London Euston, the sixth busiest station in Britain.

Radio reporter Sarah Lowther, who was on the derailed train, said two trains were “kissing each other” in a tunnel.

She spoke of a “Dunkirk spirit” on board as passengers helped one another, but said she was “worried” about the driver, who had a bad back after the crash.

Speaking to Morning Money radio, she said: “The trees were taken down from the side of the rail line last year. Trees have roots, roots hold the mud ... The mud had nothing to cling on to.

“It was the first time I’ve actually flown on a train; when we came off the tracks I assumed the brace position.

“Everyone is looking after each other with water and sugar but we’re worried about our driver.”

A pregnant woman was on board who emergency services were trying to remove from the train, she added.

Ms Lowther got on the train at 6.47am at Berkhamsted, which was hit by an “oncoming” train at 7.01am.

The worst-hit areas are across London and the south-east of England which all have amber warnings in place until 10am, according to the Met Office.

Schools have also had to close due to the downpours. Gade Valley Junior Mixed Infant and Nursery School in Hemel Hampstead, Hertfordshire, said on its website: “School is closed today due to severe flooding in the school.”

While All Saints Church of England Primary School in Didcot, Oxfordshire, said: “The school will be closed all day to day due to flooding in Tamar Way resulting in access and drainage problems. We will re-open on Monday.”

Pictures on social media show severely waterlogged rail stations and roads, including Didcot Parkway, Newbury and Chieveley stations in Oxfordshire.

Water can be seen rising up stairwells and partly submerging ticket barriers at Didcot Parkway station.

A narrow corridor west of London is expected to be hit by “exceptionally heavy, thundery rain” accompanied by hail on Friday, the Met Office said.

Met Office meteorologist Martin Combe said 32.8mm of rain had fallen in just three hours in Farnborough, Hampshire - nearly half the 70mm average for September.

He said: “The showers and thunderstorms are going to carry on for quite some time moving slowly north and eastwards, remaining around London through the morning and all afternoon in East Anglia.”

The weather front is due to send temperatures tumbling ahead of the weekend, just days after parts of the country baked in 34C (93F) heat.

There were reports of roads and properties being inundated across Surrey, Hampshire, Hertfordshire and Greater London as a band of torrential rain moved in from the Channel overnight.

Surrey Fire and Rescue Service said it had been called to reports of a house struck by lightning near Woking, while crews worked to pump water out of flooded premises across the county.

Fire chiefs advised motorists to avoid driving through flooded roads and turn around as pictures emerged of Maidenhead High Street resembling a swimming pool.

A Thames Valley Police spokesman said: “Roads are severely disrupted, including the M4 at the A34 junction with Newbury, the M40 throughout the Thames Valley and in particular the Watlington and Stokenchurch area.”