I Have just acquired a 1955 RCA CTC4 Seville Tv. Does anyone know how to disconnect the HV lead from the HV cage? It is plastic and I don't want to damage it. Any help would be greatly appreciated. Thank you..

The wire has a plug molded onto the end that plugs into the insulator looking socket on the HV cage. Grab the last 1/4" of plastic before the wire, and twist it to make sure the contacts haven't corroded together and then pull. It's normally not excessively difficult to unplug.