Damn. A week ago, I was singing the praises of Spooks. This time, I’m not so convinced. But don’t worry: I come not to bury Spooks, but to offer constructive feedback.

It’s partly my own fault for rewatching last night’s excellent BBC1 episode, which I’d seen previously on BBC3, before getting excited enough to watch another of the BBC3 previews. Exactly the same urge that compels me to have the second slice of carrot cake, the one where you realise the buttercream icing is in fact made with cheap margarine.

So, what went wrong? In a word, money. The premise of the episode — and if you haven’t sussed by now that I’ll be writing spoilers for what’s to come on BBC1, then this is your final warning — was that a big player on the London financial markets was in fact intent on bringing down capitalism for unconvincing reasons of family background.

Now, in a James Bond film I could accept such a set-up without blinking. But Spooks is, usually, cut from a different cloth (I’ll draw a veil over that dismal episode where they end up protecting the life of a rockstar a couple of series back…). Generally though, Spooks inhabits a more recognisable world than that currently inhabited by Daniel Craig.

Problem being, your antagonist was thoroughly unconvincing, a caricature of mercenary capitalism as thought up by someone whose only knowledge of it was whatever research was necessary for the episode. Not that I’m any kind of expert in such matters, as my bank manager would attest. But I’ve read Liar’s Poker, Michael Lewis’s brilliant account of life among people who make the money markets tick, and even met a few folks who dabble in that line, and by comparison the Spooks baddie was a two-dimensional twerp. His plan to bankrupt Britain was equally simplistic, all to do with destroying a Scottish bank and forcing the government to bail it out in a way that would empty the Exchequer’s coffers. There was a bit more handwaving involved, but that’s the gist.

So, the main business of the episode was somewhat lacking. Good thing that there were many commendable elements to it. Boss man Harry’s ongoing exploration of Russian penetration of MI5 saw him interrogating his elderly colleague Connie about her illicit romance with a colleague. Harry necessarily hurt Connie in pursuit of a mole and discovered a vital clue as a result. Maybe a bit quickly sketched, but this was a subplot after all, and worked at an emotional level. And in the main plot there was some grim business about what Ros felt obliged to do with the bad guy to achieve her objective, that felt appropriately ick. Ros also scored points for her behaviour when the baddy’s partner in crime had a gun to her head, proving once again that ice runs in her veins.

So, overall, a less than resounding 6 out of 10, thanks to the ineptness of the main storyline. But the other business continues to persuade me that Spooks really is one of the BBC’s best shows, and one that’s well worth keeping an eye on.