That John Paul I was murdered would strike most people as more likely than that the Duke of Edinburgh’s hitmen were closeted in that Paris tunnel, but less likely than that LBJ was in surreptitious contact with mafiosi on that grassy knoll. However, it is certainly odd that the “smiling pope” was found dead in bed after just 33 days on St Peter’s throne – and holding not The Imitation of Christ, as Vatican spin initially claimed, but papers relevant to the banking scandals that were to result in the death of Calvi and the disgrace of Marcinkus, the archbishop whom John Paul was apparently thinking of sending back to Al Capone’s home base of Cicero, Illinois.

Anyway, there’s room for a serious-minded thriller here and that’s more or less what Roger Crane has delivered. If his Last Confession isn’t as weighty or exciting as he’d presumably hoped, at least it owes nothing to the Dan Brown school of theology. It’s a reasonably responsible, moderately absorbing play stylistically indebted to Peter Shaffer’s Amadeus. It even has a former Salieri in the lead: David Suchet, giving a performance of such intelligence and calm strength that I can’t understand why he still awaits his knighthood.

Suchet is Cardinal Benelli, the pope-maker who ensured that the improbable Albino Luciani and then the unexpected Karol Wojtyla got the Church’s top job. The idea is that Benelli is making a last-gasp confession in which his joint self-accusations are that he didn’t give John Paul I the support he needed to fight a hostile Curia and that, because of his own ambitions, he dropped his insistence on an investigation into the man’s death. So David Jones’s production is a prolonged flashback, with Benelli and his papal protégé, Richard O’Callaghan’s Luciani, in conflict with reactionary cardinals such as Charles Kay’s supercilious Felici and Bernard Lloyd’s arrogant Villot.

All these men existed, though nobody can be sure that Luciani was preparing to permit birth control or that Felici, Villot and others were quite so determined to reverse John XXIII’s reforms. One trouble with the play is that, like many in which real-life figures appear, it claims authority for what is largely speculation. Another is that with Vatican smalltalk becoming Vatican bigtalk you get the impression that red hats prowl about swapping obiter dicta like “Where is the line between divine providence and human intervention?” and “Be careful of power, your punishment may be finding it”.

The dialogue can get clunky. The issues, mainly involving discipline, power and the extent to which an Eternal Church can and should change, can get laboured. And the doubts supposedly whirring within Benelli are too perfunctorily treated. But if O’Callaghan’s search for sweetness occasionally leads him to simper, he still leaves us feeling that John Paul I was a humble, gentle soul with a deep faith, a love of people and a hatred of pomp and rigid rules: which may be why, like Christ, he had to die.

Box office: 01243 781312

Editor's choice

• U2 at Nou Camp Stadium, Barcelona
• The 50 Best Movie Villains
• The 15 golden rules of theatre etiquette