It’s mortality rather than Moriarty troubling Sherlock in the absorbing drama Mr Holmes.

It’s mortality rather than Moriarty who stalks the world’s greatest detective in “Mr. Holmes”, Bill Condon’s quietly engrossing portrait of a legend in decline.

Based on Mitch Cullen’s novel “A Slight Trick Of The Mind”, “Mr. Holmes” finds Sherlock retired and living is seclusion in a remote Sussex farmhouse, caring for his bees and attended only by his housekeeper Mrs Munro and her young son Roger. Despite more than thirty years having passed, Holmes finds himself troubled by Watson’s account of his last case and seeks to set the record straight by recording his own version of events, but his advanced age and failing memory thwart his efforts to recall the events which led him to abruptly retire.

This is Sherlock Holmes as we have never seen him before. Frail, elderly and adrift in a world he no longer recognises or cares for. It’s a bold move to take such a popular character and examine him as he nears his end but the film takes its time to paint an intimate and moving portrait of Holmes’ life in seclusion. Although no longer a detective, Holmes still seeks to pursue his interests, including seeking out potential restoratives to aid his dimming memory. Told in a series of overlapping flashbacks, we learn of Holmes’ recent trip to Japan and the details of his last case.

McKellen delivers a masterful portrayal of an iconic figure, resisting the dying of the light until he feels that he has solved his final case. In the quiet and thoughtful atmosphere of the movie, the power is often in what McKellen chooses to play and not play that gives Holmes such depth and richness. His frailty is all the more shocking thanks to McKellen himself being something of a national treasure: the age make-up is superb, and the physicality of McKellen’s performance is so convincing that we are forced to contemplate the inevitability of the death not only of the character but of the performer.

Thankfully, the flashbacks provide us with some comfort as we get to see a more sprightly Sherlock in his late prime, bristling against the celebrity image of Watson’s literary creation as he takes on the case of a husband whose grieving wife has been behaving strangely. The flashbacks also give us glimpses of Holmes in situations we have rarely seen him in, from the scorched earth of post-war Hiroshima to seeing him sit in a cinema watching a melodramatised version of his own exploits. There’s a gentle theme of the legend versus the man running through “Mr. Holmes” and, in a delicious nod to the past, the black and white movie Holmes is played by Nicholas Rowe, of “Young Sherlock Holmes” fame.

Laura Linney provides a sharp foil for McKellen’s elderly curmudgeon and theirs is a complex relationship which despite the overt resentment and squabbling has a genuine tenderness at its core. Milo Parker, as Roger, is a tremendous find and he gives a terrific performance that manages to more than hold its own against the heavyweight cast he spends the time with. His is the tiny spark of inspiration that brings Sherlock Holmes back into the world and helps him to the greatest discovery of his career.

Veteran director Bill Condon wisely offers no action set pieces or token spectacle, just an intriguing nest of mysteries set against the beautifully photographed Sussex countryside. In a noisy summer of extravagant blockbusters, this is a wonderfully quiet drama. Poignant and powerfully honest, “Mr Holmes” is an absorbing drama about regret and growing old; a study in grey of the twilight of The Great Detective.