The Avengers
A Touch of Brimstone
S4 E21:
When a group of anarchists start emulating the Hell-Raisers of Regency times, Steed and Emma decide to enrol in the Hellfire Club. They overcome the opposition - and save three foreign Prime Ministers from death - but only after Emma has been elected Queen of Sin and Steed has fought a duel.
Starring
Peter Wyngarde, Colin Jeavons, Carol Cleveland