Simon Gray developed a genre of literature all his own in The Smoking Diaries, his four-volume ‘suicide note’, as some saw it, written between 2004 and his death last August. Part day-to-day log of activities, part autobiography, part wild and comic flight of fancy, the books delighted long-time fans of his wise and witty plays and earned him thousands of new ones.

To that number are daily being added many more who are enchanted, as none could fail to be, by the stage adaptation of the diaries at London’s Trafalgar Studios. This borrows the title of the third in the series, The Last Cigarette, and is the work of Gray and his old friend Hugh Whitemore who had the task of finishing the job solo when his collaborator died suddenly. This was from a ruptured aneurysm rather than the lung cancer that already had him in its grip. The irony would not have been lost on Gray.

The Last Cigarette had, of course, in life proved to be nothing of the sort. Gray was far too sensible a man to believe there was any point in quitting once the death sentence had been pronounced. On the other hand he found something grimly comic in the incongruous spectacle of fellow patients at his cancer clinic puffing away as if their lives depended on it.

Oddly, he saw much for him – and us – to laugh at in his plight, including his encounters with Welsh cancer specialist Morgan Morgan (aka “The Chipmunk of Doom”), hilariously portrayed here by Nicholas Le Prevost (left above).

In fact, Le Prevost’s main role – indeed only role – is as Gray himself. Ditto the other two actors on stage with him throughout, Jasper Britton and the excellent Felicity Kendal. In Gray’s trademark espadrilles, chinos and billowing blue shirt, they show us the writer in triplicate, taking turns to speak his words, whether coming from his mouth or from those of the characters in which he has chosen to place them.

Appropriately, Ms Kendal does most of the women, including Gray’s mum, his wife Victoria and – brilliantly – a West Indian nurse whose playwriting ambitions need tactfully to be encouraged in view of the painful medical procedure she is about to embark upon ‘below decks’ with our hero.

Classily directed by Richard Eyre, with much use of smoke effects and scene-setting back projections, and supplied with subtly understated music by the great George Fenton, this is a wonderful, unmissable show.

Until August 1. Box office: 0870 060 6632 (www.ambassadortickets.com/trafalgarstudios).