Collateral is a gripping thriller but some moments jar - on the other hand, as back stories go, a detective who had to bow out of international pole vaulting due to a mysterious 'incident' has to be up there with some of the best of them

Eastern Daily Press: John Simm plays David Mars and Nicola Walker is Jane Olive in Collateral (C) The ForgeJohn Simm plays David Mars and Nicola Walker is Jane Olive in Collateral (C) The Forge (Image: WARNING: Use of this copyright image is subject to the terms of use of BBC Pictures' Digital Picture Service (BBC Pictures) a...)

It's a state-of-the-nation drama from a brilliant playwright with a stellar cast, shot gorgeously against the stunning backdrop of a glittering London: so it's somewhat of a surprise that I haven't fallen in love with Collateral yet.

On Monday night it was a tale of two Simms as we tossed a coin – ahead of pancakes the next day – to decide whether it would be Trauma on ITV or Collateral on BBC2, both of which saw John Simm go head-to-head with himself in a bizarre piece of TV scheduling which saw his two newest shows launched at the same time on different channels.

TV bores such as myself will remember the last time this happened: in September Harry and Jack Williams, two of the most powerful screenwriters working today who are responsible for dramas such as The Missing and One of Us, saw their both their highly-anticipated shows Liar and Rellik beginning at the same time on the same day for rival channels. I blame catch-up services and that pesky worldwide web.

Anyway: should it be the psychological thriller on ITV or the thrilling drama on BBC2? I chose the path less strewn with advertisements and more full of Billie Piper, who I love: someone said to me that they'd made the opposite decision and during a spot of channel surfing during the ads had been perplexed to see John Simm in bed with a beautiful woman when seconds earlier he'd been crushed by the tragic death of his son. Simm-ultaneous hot Simm-action.

To be fair, our hero plays second fiddle to Carey Mulligan who plays DI Posh (DI Kip Glaspie, which sounds like a shelving unit from IKEA) a difficult-to-read detective who springs out of bed when the phone rings to tell her there's been a shooting on the street despite being heavily pregnant: if I'd have tried that at the same level of pregnancy I'd have needed a winch.

Written by Oscar-nominated David Hare (who Mulligan worked with on his 2014 play Skylight), Collateral is a series of inter-connecting stories which spread like tentacles from the main plot which involves the seemingly motiveless shooting of a Syrian pizza delivery man. After delivering a Quattro formaggi to Billie Piper's character Karen - who churlishly threw it in a corner when she discovered it was missing her 'special topping' – the driver was gunned down on the steps of the rather lovely mansion house of apartments.

From this moment on, the action was fast, furious and slightly confusing. We met gay female vicar Jane (the sublime Nicola Walker) and her girlfriend and the only witness to the murder, Linh Xuan Huy (Kae Alexander) who also happens to have been in a ketamine-induced haze when she saw the assailant run away and who was an illegal immigrant when rebellious Labour MP David Mars (Simm) unwittingly countersigned her student visa.

David's ex-wife and the mother of his child is chaotic Karen, who drinks too much, smokes over babies, gets overly annoyed at under-cheesed pizzas and mutters suspicious things which I am fairly sure will be key to the investigation in weeks to come. The murder victim is Abdullah, who lived in a garage with his two sisters and who was given the delivery job by pizza shop manager Laurie (Hayley Squires) who is also a carer for her disabled mother, the chap she should have given the delivery job to, Mikey, was later beaten up by nightclub heavies, presumably from the club that Linh bought her drugs from.

It's all shaping up to be interesting, and we even know – or think we know – whodunit, as we've seen the rubber-clad assailant run away, covering her tracks like a true professional because, as it turns out, she's a true professional: Captain Sandrine Shaw of the Royal Surrey Artillery, to be precise.

So far so promising – but there are moments that jar in a drama which is beautifully shot by SJ Clarkson – and it's mainly the fault of some painful, exposition-laden dialogue.

'God, I'm a mess!' said Vicar Jane, in church, just in case we thought living with your illegal immigrant ketamine-huffing girlfriend you'd asked your MP ex to vouch for wasn't emphasis enough while we were supposed to believe that TV anchor Suki (Kim Medcalf aka 'the other Sam Mitchell on EastEnders') would deliver a damning speech to David after just three dates: 'we've got to sort this out!' she intoned, before writing him an essay about why their 'relationship' wasn't working.

And don't get me started on the shoehorning of the dialogue that informed us that DI Posh used to be a champion pole vaulter but after a 'famous incident' will never, sniff, pole vault again. Beat that for a back story.

There's enough to bring me back: why aren't MI5 all over this 'Muslim shooting' like a rash? Was Abdullah the real target? Who's following Laurie? Who is the 'man in Boca Raton' who has bought the pizza parlour? And what on earth is in Billie Piper's 'special sauce' that it's absence made her throw a perfectly good pizza on the floor?