Carol Clark took groups of 15 children aged four to seven from her Big Sheep Little Cow (BSLC) farm visitor centre to Bedale railway station as part of a guided tour on local history and farming.
 
Northallerton magistrates heard that Clark, who set up BSLC in the 1980s, took the youngsters from Ripley Endowed Primary School, near Ripon, on the tour on 15 Nov 2012 and used the edge of the Wensleydale Railway line as a short cut.
 
Despite assuring teachers the line was not in use that day, a "driver experience" session was being held further down the line, which allowed untrained members of the public to take charge of the engine.
 
Hilary Reece, prosecuting, said the 67-year-old told the teachers it was safe to walk the 50 metre stretch from the station platform to a pedestrian crossing.
 
Clark, who denied a charge of trespass, told the court she had permission to walk along the heritage railway line.
 
However, Wensleydale Railway operational manger Richard Brown denied this, saying she only had permission to use Miller's Crossing to get between her two properties.
 
He added that he was horrified to discover children had been near the track.
 
"No one is allowed on the track without prior safety training, if she had asked me to take the children down there I would have said no."
 
Alan Meehan, mitigating, said Mrs. Clark had been walking along the railway line since moving nearby in 1983, and had taken groups of adults and children on educational walks by the tracks many times and had never been challenged.
 
Clark said, "I did not feel as though I had been trespassing as I have done it so many times. I was trying to explain how the community changed with the railway and trying to promote tourism for the railway. The children were managed well and I had done a risk assessment to check there were no trains running, there was no danger."
 
Found guilty of trespass, she was told by chairman of the bench, Susan Svennevig, "This was a reckless action that should never be repeated."
 
She was fined £100, with £20 victim surcharge, and £620 costs.
 
Ashley Barnard.