Two carriages, which run on the Severn Valley Railway, have had to be taken out service after they were targeted by vandals.
They were daubed with graffiti, with one, dated to 1938, covered in white paint with the word 'Banksy' written in black paint.
Another wooden-panelled Flying Scotsman carriage was sprayed with pink, green and blue paint.
Severn Valley bosses said they were 'saddened' by the vandalism, which happened between Christmas Eve and Boxing Day in Kidderminster.
The loss of the carriages means trains have been shorter than planned, disrupting the line during one of its busiest periods.
Thousands of families have flocked to the famous line, which runs between Kidderminster and Bridgnorth, over the festive period for Christmas events.
Severn Valley Railway said on its Facebook page: "Not something we wanted to wake up to, in the last 48 hours vandals have attacked some of our historic carriages at Kidderminster with graffiti. An investigation is under way.
"In light of this, some of our trains will be shorter than planned as the affected carriages will be removed from service. We apologise for any inconvenience caused.
"We are extremely saddened by this turn of events, especially in the season of goodwill.
"But, in true Severn Valley Railway spirit, we will continue with smiles on our faces and ensure the much-loved and painstakingly-restored vehicles are returned to service as quickly as possible for our passengers to enjoy."