Factual error: George Smiley stays in a hotel near Liverpool St Station, London to investigate the spy at the heart of the circus. There is one scene where we see, from above, a train leaving the station. Liverpool St station is electrified using overhead wires - the train is leaving a station using a different electrification system called 3rd rail which has never existed at Liverpool St.
Factual error: Control seems to have left behind some turntable package material for a deck called Dual CS 505-1. This model, however, only went to production in 1981.
Answer: As this story was set during the Cold War era, this was a deliberate mockery of the Soviet Union and its policies against holiday celebration and religious freedom. The entire story revolves around the prospect of a Russian Mole among the British Secret Service and Intelligence Community-at that moment, complete with a mocking Stalin Santa Claus, they were letting off steam against their reviled rivals.
Erik M.