Like “A A Gill is away” or “Martine McCutcheon is indisposed”, the explanatory legend that “Jeffrey Bernard is unwell” at the foot of somebody else’s column in the Spectator used to imply that, although the show must go on, it’s probably going on somewhere else.

Well, the play fashioned by Keith Waterhouse in 1989 from the scribblings of the absentee hack, now revived at the Garrick Theatre, suggests that the appearance of any column at all must have been a minor miracle. Bernard himself once asked anyone who knew what he was up to between 1960 and 1974 to get in touch - he had no idea himself.

Jeffrey Bernard Is Unwell is set in the preferred Soho haunt of the old rogue, the Coach and Horses pub, lovingly reproduced on a tipsy angle by designer John Gunter: faded panelling, well-worn red leatherette stools and benches, cartoons on the wall. Jeff awakes from a bacchanalian slumber in the small hours of the morning. He’s locked in. Cue a lurch towards the vodka bottle, and a rambling trip down memory lane by the original Grumpy Old Man.

Peter O'Toole, a friend of Bernard’s, delivered a sensational impersonation originally, and was succeeded after three months by Tom Conti, who now revisits the role (other notable Bernards have been James Bolam and Dennis Waterman). O’Toole looked like Bernard, a ruined Adonis whose skin was turning green from alcohol consumption and who breathed in more cigarette smoke than he exhaled goodwill.

Conti could not be more different. For a start, he plays Jeff for sympathy, something O’Toole never did. He winks at the audience. He ruffles his imposing thatch of grey black hair. He emotes quietly to the swelling Mahler music that Dirk Bogarde expired to in Death in Venice. His eyes are blackened with tiredness and his clothes crumpled, sort of. But he does not suggest a figure of minatory, frightening ghostliness. He wants too much to be liked.

This is, nonetheless, an immensely skilful performance, and Ned Sherrin’s production preserves the perfect vaudevillian tawdriness of his own original work; he has even wheeled out Royce Mills, also from the original cast, as an eye-boggling selection of quick-change characters including an old actor drunker even than Bernard, the effete painter Francis Bacon, various jockeys and trainers and Waterhouse himself, spied in an advent calendar-style upper window in a chaotic apparition of tumultuous white hair and slurred speech.

Other roles are taken by Elizabeth Payne, Nina Young and Tristan Gemmill in a portrait of the dying Soho where Bernard was such a palpable emblem. He first went there, he says, when he was 13 and it had been a downhill struggle ever since. In those days, you could become drunk and homeless for less than a pound. A life of drink, disastrous relationships with women (he was married four times) and gambling was the constant background to short-stay jobs as a stage-hand, dishwasher, illegal bookmaker and writer.

With O’Toole, there was an ineradicable dignity to all this, and a tragic dimension to his creation of a classic English eccentric, one of the greatest comic characters of our day. Conti, entertaining and likeable, gives an expert guided tour of the premises.

- Michael Coveney