Friends have paid tribute to a “life-long railway fanatic” who died after he put his head out of a train carriage window.
The accident happened as Simon Brown was travelling on the Gatwick Express at Wandsworth Common station in south London on Sunday.
Friend Reuben Smith has launched a fundraising page to help cover the costs of the funeral.
Mr Brown, originally from East Grinstead, West Sussex, first volunteered on the Bluebell Railway as a nine-year-old and had recently taken up a position as an engineering technician with Hitachi Rail Europe in Bristol.
Mr Smith, a railway conductor, said: “Railways were his life. I have known him since we were 12. It is very sad.”
Writing on his fundraising page, Mr Smith said: “Simon was a great friend of ours and a real light in the railway world. He was always smiling, cheerful and would bend over backwards to help anyone.
There’s now a massive hole in our close-knit community where he was.
“He has been taken from us at the age of 24 – it’s far too young.
“Please donate. I want to help ease the burden of the cost of the funeral for his parents.”
British Transport Police (BTP) believe Mr Brown may have been leaning out of a train door window when he suffered a blow to the head at around 5.30pm on Sunday.
Dismissing reports that he may have been decapitated, BTP said they have reported the incident to the Rail Accident Investigation Branch.
A BTP spokesman said: “The death is being treated as non-suspicious and the circumstances, including what caused the head injuries, are still being investigated.”
Mr Brown’s family have been informed of his death and a file is being prepared for the coroner.
A Gatwick Express spokesman said the train had been travelling to London Victoria from Gatwick Airport.
He added: “The emergency services attended the scene at Wandsworth Common station and, despite their best efforts, they were unable to save him. We send our condolences to his family.
“We are co-operating fully with British Transport Police and the Rail Accident Investigation Branch, who are investigating this incident.”
A spokesman for Hitachi Rail Europe said: “Simon’s death comes as a great shock to everyone and, in particular, to people who knew him and worked with him.
“Our thoughts and sincerest condolences are with his family and girlfriend. Simon joined us as a team technician at our train maintenance centre in west London in June this year and brought a clear passion for the railways to his work. He will be greatly missed.”