When the Thin and Fat Clergymen visited the Arlesdale Railway, they drove a purple car with the number plate "040 BMC". At one point they accidentally drove through a puddle and muddy water splashed onto Bert while he was pulling a passenger train.
The car is based upon a Mark 1 Austin 1100. The letters "BMC" on the number plate are a reference to the British Motor Corporation, the manufacturer of the vehicle in question.
The car is painted purple/violet with a silver/chrome bumper and silver window surrounds and door handles.