Railway enthusiasts are being urged to stay off the tracks this weekend as a historic train re-enacts the birth of the modern railway.
A newly restored replica of Locomotion No.1 will run on sections of the original Stockton and Darlington Railway line in County Durham between Friday and Sunday.
This event forms part of year-long celebrations marking 200 years since the line's opening on 27 September 1825. Locomotion No.1 was the first steam locomotive to pull a passenger-carrying train on a public railway.
With thousands expected to line the route, Network Rail warned that trespassing on the railways "poses a significant danger."
Operations director Karen Duffy said: “We want the viewing public to have a fantastic time during this celebratory weekend, but we can’t stress enough how important it is to keep safe.
“The railway is full of both obvious and hidden dangers, and it’s never acceptable for the public to trespass on to the track for any reason.
“Our message is simple: enjoy the spectacle of the anniversary journey, but please do so from one of the designated viewing locations.”

The bicentenary is also being marked with viewings of the original Locomotion No.1, an exhibition train showcasing 200 years of railway innovation, live music and entertainment.
The replica of Locomotion No.1 was taken on a test run at the Locomotion museum in Shildon, County Durham, on Thursday.
Sarah Price, head of the museum, told the PA news agency the region is having “the hugest party” to mark the anniversary.
She said: “There’s a real buzz in the air.
“People can get a sense of what it was like 200 years ago.”
The replica is “as close to the original as we can possibly make it”, she added.
“If somebody was able to time travel, they would recognise that train from something they saw.”