Some actors and theatres never disappoint- take a bow Robert Lindsay and the Hampstead Theatre. The same can be said for a handful of playwrights and Terry Johnson proves he is still one of them with funny, moving new play Prism, which he also directs.

Its main character, Jack Cardiff, is a cinematographer responsible for a string of iconic films including The African Queen, The Red Shoes and Black Narcissus but he is now suffering from Alzheimer’s. Mason, his son is fighting to keep him firmly in the present and to make him finish his memoirs.

If that sounds depressing, it absolutely isn’t. It all depends on how you see things, something Jack has spent his life controlling- using the right light, the right filter to bring out inner beauty and to help the audience see what he sees.

The unfolding of the story and its staging of the ebbs and flows of time are extremely clever. Jack Cardiff knew everyone, a number in both senses of the word, and once carer Lucy, fresh from a three-day course, persuades Jack’s angry, frightened family to just go along with how he sees the world, the fine cast transmutes into some of the Hollywood legends from his past.

I am being deliberately cryptic because I loved not knowing where this play was going to take me and that was part of the charm. No spoilers here.

The four-strong cast are all very impressive, managing accent and persona changes with aplomb and, I suspect, a huge amount of enjoyment. Barnaby Kay is convincing in each of his three contrasting parts and his journey to acceptance of his father’s own journey is at the tender heart of the play.

Outnumbered star Claire Skinner is brilliant as she always is whether on stage — one of the best Hermiones I have seen– or on TV whilst sweet, vulnerable Rebecca Night as Lucy, gives us a woman who, in her own way, is as much at the mercy of Jack’s family as he is.

So, Robert Lindsay- what an extraordinary actor he is. His portrayal of Cyrano de Bergerac, back in the dawn of time, was one of my most emotional theatrical experiences leaving me sobbing all the way home on the tube. He is quietly touching here, with emotions that flit like quicksilver and an astonishing degree of charisma.

Of course he’ll always be Wolfie to those of us of a certain age (unless he’s Foxy) – leader of the Tooting Popular Front, the TV star of fondly remembered Citizen Smith, and seeing him encourages gentle memory trips of our own, back to the 1970s. Would longer ones be so bad, I find myself asking?

Terry Johnson says in an interview in the programme — well worth £3.50 by the way– that he is at the point in his life where he is full of “The Fear” of whether he is about to slip into a final illness. This lovely play does its bit to perforate that fear for all of us.

As I left the theatre, a lady behind me remarked “Well, I adored that.”

So did I.

(At Hampstead Theatre until October 14, tickets £10-£37- absolutely bargain!)