Arthur Conan Doyle’s iconic detective has inspired a flurry of revisionist reinventions recently, but Mr Holmes, a tender, melancholy drama about the great man in extreme old age based on Mitch Cullin’s 2005 novel A Slight Trick of the Mind, might just be the most surprising.

It’s 1947 and Ian McKellen’s 93-year-old Sherlock Holmes grapples with a failing memory as he strives to reconstruct the troubling case, 35 years earlier, that precipitated his retirement to the Sussex countryside. Meanwhile, there is another mystery to solve, one involving his cherished bees and his widowed housekeeper’s bright young son (Milo Parker, very impressive).

These puzzles don’t have the fiendish elegance of the best Holmes mysteries and their unravelling proceeds at an understandably gentle pace. Yet Sherlockians will still find much to relish. McKellen is superb throughout, both as the halting nonagenarian Holmes and, in flashbacks, as the spry, supremely confident Holmes of 35 years earlier.

In a nice, teasingly self-referential touch, McKellen’s Holmes drops in on a matinee screening of a black-and-white 1940s Sherlock Holmes adventure whose camped-up, silver screen detective is none other than Nicholas Rowe, star of 1985’s juvenile romp, Young Sherlock Holmes.

Certificate PG. Runtime 99 mins. Director Bill Condon.

Mr Holmes is available on Blu-ray, DVD & Download from Entertainment One.