The Subtlest In-Joke In TV History?

In episode 1, Kim Philby's Austrian lover talks about going to Vienna and riding the big wheel, before looking down upon the tiny people below.

This immediately recalls the scene in the film The Third Man where Harry Lime rides the same wheel and muses on the people at street level.

Later, the phrase 'The Third Man', familiar as a term to describe a shadowy conspirator like Harry Lime, became attached by the British Press to the double agent - Kim Philby. In other words, this scene is a huge in-joke - talking about The Third Man to The Third Man!

There's a further irony when we consider that Kim Philby was, in an early scene of the 1980s film 'The Fourth Protocol', assassinated by a Russian agent. This agent later attempts to set off a nuclear device in Britain, and is played by... Pearce Brosnan.

Brosnan has of course gone on to play James Bond, and in Die Another Day his nemesis is played by Toby Stephens, the Kim Philby of 'Cambridge Spies'.