Every smoker in the street has looked a little different today. I'm thinking particularly of the ones gathered in troika knots outside the ITN building next to us at TLS Towers, the smoking media-types, the TV presenter, the media mogul, the writer, each tipping ash on to the pavement at an arms length from their polished shoes.
It's a familiar London scene, and not exactly like the one I watched last night a mile or so away at the Trafalgar Studios. Then, there were three smokers to watch who were actors, who wore identical clothes and who were playing the same character, the late playwright Simon Gray. This morning the groups of street-smokers are groups of different characters, wearing clothes that are only almost identical.
United as smokers, the furtive ITN folk seem, however, much more like the same person than they normally do when I pass by. Something has definitely changed. The Last Cigarette, which stars Felicity Kendal as Gray's feminine side, Jasper Britton as Gray the philosopher and Nicholas Le Prevost as Gray the literary anarchic, is no ordinary show. It is a mind-bending piece of theatre.
Smoking is not the sole subject of this play, an artfully divided and wide-ranging monologue, adapted from Gray's memoir The Smoking Diaries and directed by Richard Eyre in front of three identical desks and piles of papers.
At the opening, Gray and his wife are afraid of muggers and fail to answer the door to Antonia Fraser when she drops by unannounced to ask them for an impromptu supper with Harold Pinter.
The grave of a brother gets various visits.
The affairs of a philandering father get various revisits.
But a cigarette arrives with metronomic regularity - a suck, a mother's teat, a just-lit proof of adultery - measuring out each remembered highlight and lowlight of a dying man's life.
'Chain-smoking' gets a new and sharper sense. Theatre can sometimes do that - rearranging a commonplace into a different dramatic shape, one that does not go away.
Early in the First Act comes the news that Pinter has cancer: "And now a word from our sponsor', says Kendal: 'Simon Gray smokes Silk Cut. He is now smoking a Silk Cut. He is not feeling bilious. He has not just coughed. He is by no means on the verge of throwing up' ".
The Second Act follows the journey of the three Grays through the doctor's surgeries to discover their own cancer.
An 'opportunistic finding' in a routine medical becomes 'a grinning man holding a knife', an assassin crouched 'in a corner of the room that you've never seen illuminated before'.
In the hospital waiting rooms, where couples with holes in their throats clutch each at their own lighter, 'I wanted a cigarette so badly it was hurting'.
A bluff Welsh surgeon and a chipmunk-cheeked physician weigh out Gray's prognoses by the month - while the author regrets 'the hundreds and hundreds or thousands of cigarettes that I never experienced, inhaled and exhaled without noticing'.
Not every link in the chain of a chain-smoker is the same, the characters muse. There are 'context smokes' - 'after a swim, after a meal, after a fuck' - but better still are those not connected to an event 'the smokes of childhood which carried with them, most of all, the whiff of the smoking experiences to come'.
The Last Cigarette was written by Gray himself, his last work for the theatre before he died last August, and by his friend the dramatist, Hugh Whitemore. A mind-bender (and, maybe for some, even a mind-changer), it is acted and directed with devastating art.

