A passenger who died after putting his head out of a train carriage window was standing next to a warning notice, according to accident investigators.

Simon Brown, 24, from East Grinstead, was travelling on a train from Gatwick Airport to London Victoria when he struck his head on a signal gantry near Balham.

The Gatwick Express train was travelling at around 60mph when the incident occurred at 5.25pm on August 7, the Rail Accident Investigation Branch (RAIB) said.

The investigators' preliminary report noted that witness evidence indicated Mr Brown was standing at a door intended for the use of the train guard which has a droplight window.

It added that a notice above the window read: "Do not lean out of window when train is moving."

The RAIB found the distance between the train and the signal gantry post to be 26cm.

The full investigation will include an examination of the factors which affected the clearance between the train and the gantry and the measures in place to control the risks from leaning out of train windows.

British Transport Police is treating the death as non-suspicious.

Mr Brown was described by friends as a "life-long railway fanatic".

He 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.