TO understand Bill Condon’s film adapting Mitch Cullin’s novel “A Slight Trick Of The Mind”, it’s useful to assume that Sherlock Holmes’ birth year was 1859, the same as Arthur Doyle’s.

On the Sussex Downs, a short walk from the white cliffs, enjoying his beehives 35 years after solving his last case, Sherlock at 95 now owns a house kept by Mrs Munro (Laura Linney), mother of nine-year-old Roger (Milo Parker), whose father died early in the war.

These three characters bind stories about a marriage that collapsed between the two wars, a man from Hiroshima who had no news since his father travelled to the UK before the war and friendship and emotional and intellectual stimulation between the detective and Roger. Those periods invite arithmetically-inclined filmgoers to persuade themselves that the film’s three ages of Holmes are indeed feasible.

Without bombast, hyperbole or violence, “Mr Holmes” is an acting class given by Ian McKellen in his 76th year, a finely-crafted portrait of a man who’s spent a long life working out how seemingly unrelated pieces of jigsaw puzzles came together.

Frail of body, Sherlock often needs to write reminder notes on his shirt cuffs but remains sharp of mind.

Combining gentle comic moments and tensions, Cullin’s screenplay enhances the loneliness of a man whose colleague died long ago and whose only remaining relative died recently. The plot’s elements include a wife unable to carry a foetus to full term, a glass harmonica, a glove carrying a scent from long since, a steam locomotive rushing through a tunnel, royal jelly, a wasps’ nest. These combine nicely and logically with lovely locations, delivering convincing dramatic economy in a delightful entertainment matrix.
At Palace Electric and Dendy. Season starts July 23.