Two people were killed by falling trees yesterday as the worst storm in years battered London and the South.

A girl of 17 was crushed in a caravan where she was sleeping in Kent while a man died when a tree fell on his car as he drove to work in Watford.

A woman was seriously injured in a gas blast caused by falling trees which wrecked three houses in Hounslow.

More than 270,000 homes were without power and tens of thousands of commuters stranded by 99mph storm St Jude.

It came as coastguards called off their search for a 14-year-old boy swept out to sea.

Dylan Alkins had gone down to the seafront in Newhaven, East Sussex, with friends to watch the storm when he was hit by a massive wave. His friends were powerless to save him as he was washed away on Sunday afternoon.

The Environment Agency issued 12 flood warnings in south-west England, East Anglia and the Midlands. There are also 132 flood alerts across England and Wales.

A coastguard search was immediately launched for Dylan but called off amid “atrocious” conditions.

David Cameron said the loss of life as a result of the storm was “hugely regrettable”. He added: “We have to make sure the emergency services can act as fast as they can to help people.”

Kent police said the 17-year-old girl was killed in Hever at 7.18am. Emergency services attended the scene but were unable to save her.

The driver from Harrow, in his fifties, was crushed to death on his way to work yesterday morning. The road was closed while rescuers tried to free him from the crushed red Peugeot 307 at around 6.50am.

Passengers on a bus saw the accident on Lower High Street in Watford and also tried to help but he died at the scene despite attempts to revive him.

Ambulance spokesman Gary Sanderson said: “First and foremost our thoughts are with the man’s family at this tragic time.”

Dylan was with around 10 friends when tragedy struck. One wrote on Facebook: “A massive wave came and washed him out in front of my eyes there was nothing we could do apart from wait, he was in the water for about two hours.

“Dylan was a very good mate of ours and had some very funny memories and he will be missed and loved by loads of people rip little man x.”

His grandmother Carroll Alkins, 55, said the family was devastated. She said: “It’s very raw, as you can expect. We don’t really know any more. It’s very hard.”

Football-mad Dylan, who went to Tideway school, had lived in Liverpool and Lewes before moving to Newhaven with his father Danny and younger brother.

In London a man in his 50s was taken to hospital in a neck brace after a tree fell on his van in Ealing, while another victim, aged 26, was hit by part of a falling tree near Clapton Common early yesterday morning and taken to hospital.

A 29-year-old man was hit by a tree in Ealing just before 6.45am and treated for head, chest and foot injuries before being taken to hospital.

The gas blast at 7.45am in Hounslow left an elderly woman with “life-changing injuries” while two other people were treated in hospital for cuts and bruises. Search and rescue teams with sniffer dogs were going through the ruins for a couple who were unaccounted for after the explosion in Bath Road.

The emergency services were trying to establish if the couple were at home when the incident happened. The explosion blew apart three houses and damaged a fourth. Twelve people were evacuated to a nearby nursing home. The blast damaged properties up to 50 yards away. The blast is believed to have happened after a tree was blown over, fracturing a gas mains and causing a leak.

Niraj Bhati said: “I have never heard anything like that explosion. Windows were smashed, it was horrible and very scary. Two old women came out of the ruins and one seemed injured.”

Ross Ellis, 40, a hospital manager said: “I thought it was a car bomb. It was a huge bang. I looked out of my window and two old ladies were coming out of the wreckage. One had blood over her and there was a zimmer frame next to her. It was a horrible scene.”

Krishna Chevendra, 40, whose house backs onto the destroyed homes said: “It was like a bomb going off, my windows were blown out. My kids were crying as we took them away from the house, it was carnage.”

Firefighter Matthew Burrows said: “There was a gas leak but whether that was caused by the tree falling we do not know yet.”

Three family pets were saved from the wreckage by firefighters after being stuck for three hours. In Leyton the storm tore down scaffolding covering an entire street. The 62 yard-long structure collapsed at around 6am blocking Francis Road with wooden planks, metal poles and plastic sheeting. It is understood a number of barrels of acid to clean the scaffolding were being stored on it when it fell. Nobody was injured but several cars and lamp-posts were crushed. Some of the terraced houses were also been damaged.