[Vintage_RC]

This is likely to be based on a synchronous motor which means its time reference is the mains frequency. In the UK the frequency is on average 50Hz although at any specific time it may be slightly higher or lower. The condition of the mains cable should be checked and also the termination of the cable inside the clock. If the synchronous motor's winding is OK it might be run, if it is open circuit it would be easier to replace the mechanism with on of the cheap quartz movements. To be honest I think the easiest and safest thing is to go for the quartz option.