This high-concept World War III bunker story is much better than I remembered. There’s a psychological element in that once again Cathy appears to be confronted with the possibility that Steed is not the man she thought he was, but in the sense that he is a traitor rather than a double (as in The Man With Two Shadows), while Steed and Cathy play out roles as they did in Brief For Murder.

The whole concept is larger than life, set in the cartoonish world of a secret government bunker, infiltrated by a beautiful escapologist in a wetsuit who makes deft use of what must have been the fairly modern concept of CCTV blackspots. The heavy debating of World War III seems rather dated, belonging to the cold war era (or it would have done a few weeks ago, before Russia annexed the Crimea). DISCO is certainly not the last use of comical acronyms – nor the last boss figure to have an incongruously whimsical title.

Steed is tortured in this episode (giving Cathy an opportunity to frown her liberal disapproval) and it’s because he’s always so impeccably dressed that seeing his collar wilt and his top button undone is so shocking. It’s an episode that proves that just because The Avengers has veered away from gritty doesn’t mean it cannot do dark and twisted.

Steed seems to have a different flat. Nice big windows. Is this still supposed to be 5 Westminster Mews?

There’s no champagne, but Steed seems to take milk in green tea. Can that be right?