A train driver had to stop his locomotive to avoid hitting a boy playing on a railway line in Oxfordshire.
Phil Marsh took a photo of a boy on the tracks while a woman nearby stood by on a phone in Chinnor.
Mr Marsh, who has worked on the railways for 46 years, said he took the picture to highlight the dangers of trespassing on tracks.
He said trespassing on train tracks is “happening more and more” in the area.
“It’s very dangerous,” he said. “A young lad [was] putting a stone on the railway line.”
Mr Marsh said he was driving slow enough to stop the train in time, but added a 200-ton steam train travelling at a maximum speed of 25mph would usually take “at least 100 metres to stop”.
He said people trespassing on the heritage rail line between Chinnor in Oxfordshire and Princes Risborough in Buckinghamshire was “very prevalent”.
People stand “in between the rails, videoing or photographing the approaching train and simply expect you to be able to stop”.
The heritage rail line was reopened in August 2018, allowing passengers to take a steam train from Chinnor to connections with mainline services to London.
The line had last offered a passenger service in August 1957.
On Saturday, Mr Marsh said a drunk man was found on the tracks by a volunteer moments before a “murder mystery” train was due to pass through.
A survey of 1,000 teenagers across the UK carried out on behalf of Network Rail showed 18% of them did not know walking along railway tracks was illegal.