A doctor whose teenage patient died after inhaling a cocktail of toxic gases has urged other youngsters not to forget the “tragic lesson” of his death.

Ham & High: Joseph BennettJoseph Bennett (Image: Archant)

Dr John Brook encouraged young people to take heed of 17-year-old Joe Benett’s death, as he prepares to tackle a gruelling 100-mile charity bike ride in memory of the Hampstead schoolboy.

Joe, who attended University College School in Frognal, died in September 2012 after breathing in a mixture of dangerous gases from a spray can at a friend’s house one Friday night.

He wrongly believed the aerosol contained nitrous oxide or “laughing gas” – a popular drug for some teenage party-goers – but it was instead filled with toxic substances including butane, which is used as lighter fuel, and pentane, which is used to make polystyrene.

Dr Brook, who was Joe’s family GP for most of his life, said: “As a doctor you expect that people die, but you don’t expect lively 17-year-old, healthy people to die, in such tragic circumstances.

“I try very hard to make young people aware of the risk of drugs and what could happen to them, if they either suffer a side effect or a catastrophe.

“This is a tragic lesson that I hope young people will remember – and not look at it as just something that could not happen to them. The impact it has had on his family and friends is just so devastating.”

The 68-year-old, who himself has three grown-up children, is riding the London Bikeathon, a 100-mile route that takes in several tough climbs ­including Box Hill in Surrey, on August 31 – the same date that Joe inhaled the gases in 2012.

The teenager, who lived in West Heath Drive, Golders Green, suffered convulsions and a cardiac arrest, went into a coma, and died four weeks later on September 27.

Last May, a coroner ruled that his death was accidental.

Dr Brook, whose private practice is based at his home in ­Oakhill Avenue, Hampstead, has so far raised more than £15,000.

The money will be split between the charities Leukemia & Lymphoma Research and St John’s Hospice, which is connected to the hospital where Joe died – the Hospital of St John and St Elizabeth in Grove End Road, St John’s Wood.

The doctor, who has previously completed six marathons, added: “He was a very lively, interesting, kind and very well-liked young man, and I was devastated for his family, but also very upset personally, because I had known him for such a long time.

“I will never forget him and this is just a way of me remembering him.

“He just had a sort of enormous zest for life, and he was such a pleasure to look after and a fun person to deal with as a doctor, and that made it so much more devastating when the tragedy happened.”

n Visit justgiving.com/John-Brook2 to support Dr Brook’s cycle ride.