SPOILER ALERT: This blog is for those watching series one of Partners in Crime. Don’t read on if you haven’t seen episode one.

David Walliams and Jessica Raine star as Tommy and Tuppence Beresford in this stylish Agatha Christie mystery romp, which was once before adapted in the early 80s with Francesca Annis and James Warwick in the title roles.

It’s a thoroughly British crime adventure about a nice middle-class married couple blundering into a The Lady Vanishes-style spy mystery one day on a train home from France. As Tuppence’s curiosity leads her into deeper and deeper trouble, the hapless Tommy can’t help being swept up by her determination to solve the puzzle. And all while their son George is away at school.

Anyone not prepared to put aside the Beresfords’ obvious privilege and lack of real problems, pick up your coat and hat and leave now. This is a museum piece designed for the purposes of escape and may annoy those wishing for social realism. You’ll get some cold war chit-chat over tea and buns but these are, strictly speaking, very beautiful crosswords.

Back to three across. A young woman called Jane Finn behaves oddly on the Beresfords’ train and then promptly vanishes, pursued by men who assassinate her boyfriend. Tuppence takes Jane’s abandoned notebook and can’t stop thinking about the strange encounter. We, of course, see Jane hiding something in Tommy’s bee box, presumably the secret recording that the British secret service is so keen to get their hands on.

Finally back in England’s green and pleasant land (it’s raining, obviously) Tommy and Tuppence mull over what happened. While Tommy tries to deflect his wife’s curiosity, she is more than keen to follow the scent. Beyond this, I can’t work out who they are yet, but I want their house. Every last armchair and door handle. And those round windows. I can see I’m going to get increasingly distracted by the decor. Their English home is eye-achingly pretty.

We do know that Tommy is a bit of a silly boots, always knocking things over or being knocked over himself by runaway catering trucks. He puts household bills in the bin and doesn’t read the instructions for things. Walliams is good casting but you can tell he’s trying to keep a lid on Frankie Howerd and give this performance a control and subtlety we’re not used to seeing him deliver.

Before you can say “new het” Tuppence is knee-deep in an illegal gambling den, rather primly placing a bet on the favourite in the 12.30 at Catford. She finds herself grasped by the throat when she stupidly reveals herself to be in search of the missing Jane.

Tommy is visiting his uncle, Colonel Carter (the rather adorable James Fleet) who works in the department of secret things at the ministry of hush hush. He reminds Tommy that “Just about every endeavour you embark upon ends in disaster.”

“Where did you learn all this?” asks an exasperated Tommy as Tuppence drags him on a wild chase away from the henchman tailing her since the gambling den. “John Buchan, Conan Doyle, Dorothy L Sayers,” she replies, offering the most obvious metaphorical wink to camera so far about the derivation of this tale.

As characters they’re starting to plump out nicely but I’m yet to get that zing of chemistry that should be evident between a married pair. I hope Raine’s rather chilly introduction and Walliams’ goofery soften a little as the series goes on so we actually get to see what they’re like as a romantic couple. On this first episode, I’ve yet to be convinced but I’m willing to invest.

When Tommy’s uncle, Major Carter, comes to dinner he tells them everything. The man shot on the train was one of his agents and they must get hold of that recording before the Russians do. No longer the nice, middle-class couple who make honey. They’re now real spies. It’s all completely far-fetched and also the kind of delightful escapism which makes me click my heels in mid-air.

I mean, the code word to help them recognise other friendly agents is “200, all out”. It literally is cricket. None more British.

To complete the triumvirate, we meet Tommy’s old army friend Albert, once a soldier and now their Doctor Watson, a school science teacher with a fully equipped lab and dark room. Stroke of luck when it comes to developing those negatives.

They are almost constantly followed by villains in cars, quickening their step and trying to remain calm. It is all very Buchan and has the charm of any adventure wherein ordinary folk become embroiled in espionage. It should be called Tommy and Tuppence Are Out of Their Depth because that’s basically what we’re going to get every week. Happy with this.

While an emboldened Tommy follows his wife’s attacker into another darkened doorway marked Live Peep Show, she poses as the secretary to a self-obsessed opera singer who is also connected to this mess. (Played by the brilliantly clipped Alice Krige in full diva mode.)

As the episode reaches its climax, both Tommy and Tuppence are about to be rumbled by their respective targets. How will they get out of their collective jams? And where can I buy their furniture?

Case Notes

• The only clue to T & T’s chemistry is his playful “Any time you wanted to play the part at home … ” when he sees her disguised in blonde wig and red lipstick. He sounds more like a muted Carry On character than a man genuinely inflamed. Will they really be able to convince as two people who share a sex life?

• The set dresser is trying to kill me with envy. Every place setting and sideboard is neat perfection. I’m in this as much for the eye candy as anything else.

• There was a glimmer of Walliams unleashing his suave in this first episode.

• As his confidence grows as a spy, I’m hoping this side of Tommy takes over, because he can’t forever be knocking over vases and so on.

• That guy who roughed up Mrs Beresford in the gambling den is the same sheepish chap who basically caused the boat to sink in Titanic. I knew I couldn’t trust him from the off. (He’s the excellent character actor Jonny Phillips.)

What did you think of episode one? Will you be back next week? Let us know your thoughts below.