Pictured: Boy, 13, lying in coma after school corridor 'happy slapping' attack left him needing life-saving surgery 

A 13-year-old was left in a coma and suffered brain damage after a bully punched him repeatedly in a 'happy slap' attack at school.

Tommy Allery, 13, was filmed as a thug beat him over the head in a school corridor in Hertfordshire while four others watched. 

Footage shows the bully saying he will 'finish him off' before punching him in the temple – he collapsed 20 seconds later with a seizure caused by a brain bleed. 

Tommy, who is said to have kept his hands in his pockets throughout the beating, then had to wait 30 minutes for an ambulance because the school said the case was non-urgent. 

The teenager needed a wheelchair and had to be fed through a tube during his slow recovery.  

Tragedy: Tommy Allery spent several weeks in a coma at Great Ormond Street Hospital after a 'happy slap' attack at school left him brain damaged

Recovery: Tommy in a wheelchair in hospital being fed through a Tube - he still needs physiotherapy every week and needs fluid drained from his major organs

His family say it has wrecked 'the best years of his life' and he will never be able to drive, fly or play his favourite sports ever again. 

He also now needs physiotherapy every week and has been fitted with a shunt that drains fluid from his brain, heart and stomach.

His mother, Clo Marques, told The Sun: 'I feel like I'm grieving for my son. I'm never going to get my Tommy back. I've got this new Tommy, but not my old one. I miss him so much.

'I know he'll never be the same Tommy he was. He should be out chasing girls but he's just at home in bed all day. It's ruined the best years of his life.' 

She had rushed to the school and found Tommy still lying on the floor, fitting and shouting 'cut my head off' because of the pain. 

Harrowing photographs show the damage caused by the 'happy slap', including Tommy lying stricken in a coma.

He has lost his short-term memory, which could take up to two years to return, and will never be able to drive, fly or play contact sports. Tommy has also lost around four stone and had to be fed through a tube.

The teenager who attacked him, who cannot be named for legal reasons, admitted GBH at St Albans Youth Court on May 4, according to The Times. 

Video footage of the attack shows the bully throw three punches, while someone off camera shouts 'rudeboy'.

The bully and his friends ran off but another boy tipped off a teacher, who called Tommy's mother. 

Eventually an ambulance arrived and Tommy, who had begun vomiting, was tranquillised on the way to Watford General Hospital.

A CT scan showed a bleed on his brain and heavy pressure in his head so emergency surgery was required.

Tommy Allery, 13, with his father John, who said 'I just burst into tears when I saw him in the recovery room'

Later he was sent to Great Ormond Street Hospital's neurosurgery unit for more life-saving operations and remained in a coma for 12 days.

His father John Allery, 48, said: 'I just burst into tears when I saw him in the recovery room, I couldn't handle it. His mum stayed by his side the whole time, I don't know how she did it. She was so strong.'

Tommy had five more operations during his three month stay at Great Ormond Street and was twice declared dead.

Brutal: Tommy was repeatedly beaten - but a final blow to the temple is believed to have caused the damage

His father said: 'I was calling his name and screaming 'Tommy, can you hear me? Squeeze my hand if you can hear me. But he couldn't respond, he couldn't talk or move, he was just lying in my arms. It was horrible.' 

His school has denied that they failed to take it seriously - but described it as an altercation rather than a beating caught on film.

Its headteacher said: 'An altercation occurred between two Year 9 boys at the end of school on the afternoon of 6 January 2016. The incident resulted in one of the students being punched and subsequently taken to hospital with a serious head injury.

'The school immediately called ambulance service, accurately describing the apparent nature of the injuries to the student. At no time were the injuries either exaggerated or downplayed.

'The altercation in January was an isolated incident and there is no evidence that similar violent or disrespectful behaviour is prevalent in the school.'

The ambulance service confirmed that they had classed the call as 'non life threatening' based on information from the caller. 

A spokesman for the East of England Ambulance Service said: 'We received a call on 6th January at 3.37pm to reports of an incident in [Hertfordshire] to which we sent one ambulance crew.

'The call was coded as a 'green' – serious but not life-threatening – call, based on the information provided by the caller.

'The green call requires an ambulance response within 30 minutes and in this case we were able to get an ambulance on scene at 4.07pm. At the scene, a teenage male was treated for a head injury before being taken to Watford General Hospital'.