A royal visitor is coming to inspect Bletchley Park, but the top brass are worried that this particular royal is a Nazi sympathiser. Hut 33 has to delay him and make sure he doesn't see any of the code-breaking machines.
Allow me to fill you in on how and why this episode came together without, hopefully, deconstructing the whole thing into a joyless series of components.
The Inspection Episode
The 'inspection' episode is common sit-com device and also a very useful one. Characters are sent rushing around getting things ready. Cleaning, polishing and tidying. In the process, skeletons can be found in cupboards, difficult tasks can be comically compressed and plenty of dirt can be swept under the carpet. See the effect of the Inspector in JB Priestley's An Inspector Calls. The presence and prospect of an Inspector causes lives to unravel.
Another advantage of the 'Inspector' episode it is simplicity. Simplicity is everything in comedy, especially in half-hour sit-com. If the audience is confused, even slightly, they can't laugh. In that sense, sit-com is contrived reality, over-simplified and sign-posted. The audience is normally happy with this because they understand the genre. The trick is, within the contrived situation, to make the plot and events seem as organic and un-contrived as possible. We start with something believable, and through a series of believable steps end up somewhere original and bizarre, so we're left thinking 'How on earth did we get here?'!
Inspections are a reality of life - audits, royal visitors, tax men - so we have a believable, clear goal that we can all understand - everything has to be ready for the inspector or special visitor. It's a variation on 'The Boss Comes to Dinner' episode that's common to many domestic sitcoms.
The trick of sitcom, then, is to take a familiar situation and push them further, into unfamiliar areas. World War Two threw up plenty of these. And so when I came to consider the inspection episode, I tried to think of what the twist would be. As the blurb of the show suggests (so I'm not spoiling it) what if the Royal visitor cannot be trusted?
This taps into the very real concerns during the war that some members of the aristocracy could not be trusted and were well-known for Fascist sympathies. It is a running theme of the series - partly embodied in the character of Professor Charles Gardiner. As a well-connected Oxford professor, he moves in elevated circles and was friendly before the war with high-ranking Nazis and sympathised with some of their views. Every episode, Archie normally makes jokes implying that Charles played some kind of gentle sport with a prominent Nazi. And Charles has to concede that he was friendly with the Von Ribbentrops, the Rommels and even Mussolini.
And so as I was thinking about which Royal visitor, real or imagined, could visit Hut 33, I stumbled across Prince George, Duke of Kent. If you read his profile here, you will see that he was a very worrying figure for the British Establishment. Given the extraordinarily secret nature of the work at Bletchley Park, the Prince's visit would have to be frustrated in some way. If news of the breaking of Enigma was leaked back to Germany, it would have proved disastrous for the Allies.
German High Command had no idea that the British were reading their messages so a hint to that effect would have been catastrophic for Bletchley. 1941 was a difficult year for the Allies. Britain stood alone against Germany and was on the verge of starvation. The convoys in the Atlantic bringing food and supplies from America were a lifeline. This, then, gives an intensity to the story that hopefully makes it play and gives good motivations for our regular characters who are instrumental in keeping the prince away from the code-breaking machinery.
Fans of Radioactive will recognise the voice of the Prince. He is wonderfully played by Michael Fenton Stevens (who also played alongside Robert Bathurst (Charles) in My Dad's the Prime Minister).