The first reel of this film is very deceiving: you might well think that it's a kind of dramedy, a clichéd story of a do-gooder yuppie activist expanding his horizons and finding his humanity through an acquaintance with a very quirky homeless man. But it's absolutely nothing of the sort. To judge by interviews with BBC producers, the director, and writer Alexander Masters, the final film matches the intentions they had from the start, to make something that wasn't easy and which captured this man Stuart Shorter in all his complexity.
Master's script is really compelling & tight. But it's the actors who drive the film: Benedict Cumberbatch and Tom Hardy together, more often than not in fairly tight sets merely talking. They were already both masters, back when this was filmed.
Tom Hardy's role here bears a vague resemblance to his work in Nicolas Refn's film Bronson; though I'd say that this film is even bleaker and more harrowing than Refn's. The eruption of Stuart's pain and self- hate is shocking, and Hardy doesn't ever hold back. The performance compares well to that of Robin Williams' in The Fisher King. In both cases, the actor enters a state that shocks you into concern for them rather than sitting in admiration of a modulated performance.
This is an incredibly bleak and brutal film, without the comfort of its having been a fiction.