London Spy, BBC Two

Penned by Tom Rob Smith, the author of Soviet-era thriller Child 44, London Spy imparts unexpected spin to the espionage genre. Among other things, apart from the title it was by no means clear that it had anything to do with spies for virtually all of the first episode, although the camera did linger suspiciously over the MI6 building on the South Bank at one point. And once, the protagonists spotted a dubious-looking car in their rear-view mirror.

However, just before the final credits rolled, we suddenly knew we'd been plunged neck-deep into something exceedingly sinister. Danny (Ben Whishaw) was, as far as he knew, involved in a fairly stable relationship with Alex (Edward Holcroft), a painfully reticent fellow who worked for an investment bank. Imagine his shock when a policewoman told him that Alex was really Alistair, and the few facts Danny thought he knew about him weren't true.  

Sado-masochistic sexual activity cannot be ruled out

Art appears to have imitated life somewhat, and the alarming scene when Danny stumbled across a body packed inside a trunk – the panic on Whishaw's face felt horrifyingly real – was surely indebted to the real-life story of MI6 employee Gareth Williams. His rotting remains were found packed into a sports bag in a Pimlico flat in 2010, and the police somehow managed to conclude that this was "probably an accident". And to be fair, which of us hasn't inadvertently locked ourselves inside a piece of luggage from time to time? However, the coroner didn't agree, and a former KGB agent claimed that Russia's Foreign Intelligence Service was involved.

As for our fictional cadaver, at the moment we don't know whose it is or what happened to it, though it seems sado-masochistic sexual activity cannot be ruled out. But before all this suddenly turned the narrative inside out, London Spy had been a slow-burning but engrossing story of how Danny, a rootless young man who works in a warehouse by day and goes clubbing by night, first encountered Alex as he staggered home by the dawn's early light, evidently feeling like the sole on a worn-out shoe. Danny subsequently engineered another meeting (their first having been on Alex's jogging route), but getting to know Alex was like trying to unravel the mysteries of the Enigma machine using only a paper clip and a lump of Blu-Tack. Yet, despite not even having written down Danny's phone number, he suddenly turned up at his front door, and their fragile, fragmentary affair was launched. 

There are four more episodes to go, but Smith seems to be drawing us into a milieu where the looking-glass war of lies, feints and disinformation infects the private realm as much as the institutional one. Jim Broadbent (pictured right) plays Scottie, an older gay man who works in some unspecified Whitehall department, and he has been Danny's friend, conscience and salvation, but (to his chagrin) not his lover. Broadbent's mix of frustrated longing and paternalistic concern are subtly matched by Whishaw's neediness and frailty, while Holcroft presents a smooth facade of almost robotic remoteness. We await further developments eagerly.