Moscow's planted a mole. It is one of five men. Does that not just thrum at your heartstrings? I would love to snag a PSL based on the genre. It can be about two or more friends, where one is an agent of influence for Kremlin, and at least one of the friends is a member of MI5. Alternatively, we can restrict it to MI6 and bring it closer to the source material; or even canon, if you've read the books. These are just rudimentary ideas, but I really don't mind an overhaul of the premise, so long as the flavour is there!