A maths teacher told police who caught him with a prostitute in his camper van that he was a trainspotter who got lost in a red light district.
David Kevin Harris, 43, of Newport, south Wales, who denied soliciting, was stopped in Wolverhampton after officers saw the woman get into the vehicle.
He told police he had got lost after travelling to see a special locomotive at the Severn Valley Railway.
He was fined £350 with £300 costs by Wolverhampton magistrates.
The court heard how police saw Harries sitting in his Mercedes camper van which had a makeshift bed in the back, and facilities to make tea and coffee.
He was in Powlett Street in Wolverhampton at night when an undercover police vice patrol passed by.
Officers saw a woman getting into the vehicle and Harries driving off.
Harries told the court he had travelled to the area to see a locomotive, but he had got lost and stopped to make himself a cup of tea.
He said the prostitute jumped into the car.
"She said, 'drive drive' so I thought she was in some kind of danger," he said.