CCTV recorded three men damaging an electronic barrier in the Market Place public toilets in Market Yard.
The incident happened between 2.30pm and 2.45pm on Sunday 29 November 2020.
The men have been described as aged between 19 and 25.
PC Gabrielle Slaney said: “This was mindless vandalism that will cost the local council a considerable sum to repair at a time when public finances are stretched.
“It occurred in broad daylight and we would like to hear from anyone who may recognise these men.”
Anyone with information should contact 101 quoting reference 20*631795.