Rowdy trainspotters desperate to see the iconic Flying Scotsman as it tours the UK have been causing chaos on the tracks.
Keen to get the perfect photo of the world's most famous steam locomotive they have put themselves at risk.
Now police and rail bosses have been forced to issue an urgent warning to train fans over fears someone could be killed.
The Flying Scotsman tours the UK throughout the summer, with a tour from London Victoria through Surrey and Sussex on Saturday.
Trainspotters have been putting their heads out of moving trains and walking onto live tracks
But to avoid mayhem at certain locations, Network Rail have not published details of the route.
They say that as well as sticking their heads out of the windows of passing trains people have also walked onto the tracks.
With a live conductor rail switched on at all times bosses say the risks of death when trespassing on the tracks is high.
Chief Inspector John Justice, from the British Transport Police said: "So far on the Flying Scotsman tour there has been some disruption, with various incidents of trespass along the line.
Rail bosses say the risk of death when trespassing on tracks is high
"It is incredibly disappointing that despite repeated warnings, people chose to risk their lives and the lives of others by going onto the railway tracks to view the Flying Scotsman."
Andy Derbyshire, of Network Rail South East route, said: "It's great that people want to come and see the Flying Scotsman but it's important for them to stay safe.
Trespassing on tracks could see offenders get a criminal record and a fine of up to £1,000
"In the South East, the conductor rail that sits next to the track carries enough electricity to kill people and it is vital that rail fans stay in safe areas and don't trespass on the line.
"I would also ask passengers to refrain from putting their heads out of the windows as the train runs along."
Mr Justice said: "Anyone found trespassing on the railway will be dealt with according to the law - you could be brought before the courts, get a criminal record and a fine of up to £1,000."