How irksome in some ways for the National Theatre that both the glamour and the accessibility of cinema have bookended its first 50 years, when the company and, latterly, its Southbank home, are essentially driven by and dedicated to live performance. But it was Laurence Olivier’s film career, making him a household name, which helped secure for him the job as first director of the National Theatre in 1963. And it is cinema relays that have taken NT productions to places and people who might never step into Denys Lasdun’s building, despite the company’s national ambitions.

We have plenty to be paranoid about in the most surveilled country in the world. British contributions to the conspiracy thrillers that bloomed so fruitfully in the US around Watergate have, though, stayed slim. Maybe that’s one reason Closed Circuit’s extreme Secret Service behaviour in the aftermath of a bomb atrocity at London’s Borough market feels so fake.

CIA agents snuffing out inconvenient people on city streets is cinematic second nature. MI5 hunting Eric Bana and Rebecca Hall’s high-powered barristers through Dalston back-alleys takes more swallowing. So does some of the dialogue in Steve Knight’s bumpy script, despite having Jim Broadbent, Anne-Marie Duff, Ciaran Hinds and Julia Stiles to help speak it.

Bana and Hall (pictured right) are excellent as ex-lovers Martin Rose, the defence for surviving bomb plotter Farroukh Erdogan (Denis Moschitto), and Claudia Simmons-Howe, the Special Advocate defending him in closed court. The potential for abuse and fundamental unjustness of the latter process when dealing with alleged terrorists is one of the film’s most fascinating themes, if it only had the courage to stick with it. Aussie Bana particularly enjoys Rose’s blowhard articulacy, barely hiding bitter vulnerability after a work-wrecked marriage, and theatre aristocrat Hall (Sir Peter’s daughter) matches his comfort at posh, powerful sparring. Riz Ahmed’s nervy, dangerously idealistic MI5 man, Ann-Marie Duff as his venomous boss and Jim Broadbent’s oily Attorney General (pictured below), with so many Tory and New Labour apparatchiks to inspire him as he bullies and lies with a beaming smile, are also fine. But though writer Knight’s work include London thrillers Eastern Promises and Dirty Pretty Things and Brum gangland saga Peaky Blinders, there are leaden lines the cast deserve danger money for lifting.

Closed Circuit’s head-thumping improbability as a thriller also stands in stark contrast to its great efforts at legal realism. MI5’s reasons for a post-bombing cover-up which develops into an attempted mid-trial massacre of anyone who knows what they’ve been up to are convincingly extreme, and the idea of British agents being so ruthless on British streets is usefully challenging. James Bond’s sprint down Whitehall to protect the liberty of the British state in Skyfall is turned inside-out. But when the intended victims are Julia Stiles’ top New York Times reporter, and Bana and Hall’s elite lawyers on what is repeatedly called the Trial of the Century, Stalin’s KGB seem better candidates for the job. As blundering hitmen attack our heroes the night before the trial, a phone-call to any newspaper would make their deaths instantly unthinkable. D-notices be damned. They’d have to blow up the printing presses (and the internet) to stop that coming out.

Director John Crowley’s previous film Is Anybody There? combined bleak, comic and sentimental moods as Michael Caine declined in an old people’s home. Closed Circuit feels compromised and half-cooked. Walking out of one of Closed Circuit’s inspirations, the fine British conspiracy thriller Defence of the Realm, in 1986, newsstand headlines of the nearly government-toppling Westland affair greeted me, and film and murky reality seemed to merge. No chance of that here.

Overleaf: watch the trailer for Closed Circuit