Perhaps the quality of a first-of-its-kind filmic undertaking can be measured by how quickly one forgets the novelty. The headline of writer/director/producer/star Woody Harrelson's piece is surely that a film has now been made not only in real time, with a single camera, but also streamed live to cinemas while its actors sparred, its musicians played and its jokes were deployed. The hundred minutes of action are adapted from some real-life headlines: Harrelson's 2002 misadventures which included a taxi chase, arrest for criminal damages and a regrettable philanderous jaunt. So why does someone choose to enact a cinematic feat whilst dramatising the worst night of his life, and then play it for laughs?

Before we even get to the 'why', I'll admit that it sounds risky, sketchy (see the uninspiring poster) and narcissistic. But I'm impressed by the chutzpah it takes to work in the face of those risks. Considerable theatrical skill is required by the cast to present the piece without cuts, and the technical crew deserve awards for the staging, blocking, temperamental transmitters and the visual grace achieved amid miles of cables. Not to mention the BPM their hearts presumably reached. A pre-feature segment shows rehearsals during which one transmitter failed, leaving the cinema screen blank – no wonder there's also a showreel of friends such as J-Law and McConaughey telling Harrelson how mad he is.

After these joshing naysayers, the story unfolds – a sparsely attended play, a tabloid scandal to conceal from his wife (played by Eleanor Matsuura), and some fair-weather friends picked up in a restaurant. The lumbering Woody has to be home by midnight to make amends, thence to take his daughters to "meet Harry Potter" (at Leavesden Studios) and prove himself to be a functioning human being – but not before enjoying "just one drink". The film begins skewering the vapidity of fame and the media, and then sustains a character assassination of its leading man, all the while being funnier than it has any right to. Owen Wilson plays a believably vain version of himself, doing so well at counselling his friend that punches are eventually thrown. The lavish, subterranean party (eventually cut short by the Law) is a wonderfully designed space – indeed, things seem to be going on beyond the natural realm as incantations and a Saint or two materialise from the event's 'Hippie/Gypsy' aesthetic. Throwaway references to Dante are getting at something – and the piece's unexpected 'spiritual quest' dimension is well served by 'just turning up' in the heady, convincing flow of that single-camera gambit.

Back to the now long-neglected 'why': Lost in London's form aptly follows its narrative flow. Both are designed by Harrelson to show how easily he lost control in a situation of his own devising. The character tries to play upon his dim-nice-guy persona to get out of that escalating dilemma: the actor/director manages to get by on that charm while satirising it. And there are flaws, including a fairly claustrophobic and unfunny section heavy on men-being-shouty, and the ending's openness to an interpretation that all should be forgiven. But I enjoyed the comedy moments, briskness, layers of detail… before remembering the film's assumed place in history.