Sheila Sim, Lady Attenborough: Winsome actress who gave up her blossoming career to provide a 'cocoon' for her husband, Richard Attenborough

The death of Sheila Sim has brought to a close one of the great love stories of British cinema. A winsome, pleasing actress who put aside a blossoming career in order to give her husband, Richard Attenborough, a stable, calm foundation on which to build his remarkable career, their 69-year marriage had more than a touch of the fairy-tale about it. Having met at Rada, they quickly became inseparable. Until she gave up acting, Sim often appeared in movies with her husband, but never as merely a talisman; in her own right she brought charm and panache to anything she appeared in.

Sir David Puttnam described Sim as creating "a cocoon of security" around her husband, and insisted that "Richard Attenborough couldn't have been who he was without Sheila". It was a great tragedy that for two people of such industry and rectitude, their final days were so frail; Attenborough, after suffering a stroke, moved into Denville Hall, the retirement home for actors, to accompany Sheila, who suffered from dementia in her final years, both of them at the end requiring full-time carers.

Sheila Beryl Grant Sim was born in Liverpool in 1922, one of two children born to Stuart, a First World War veteran and an employee of Barings Bank, and his wife, Ida (née Carter). The family moved to Surrey, where she attended Croydon High School; her younger brother Gerald would also go on to train at Rada, before enjoying a busy career on stage and screen.

She met her future husband in 1940, and they fell in love while playing in a college production of The Lady with the Lamp. Attenborough's rise to fame was swift; his first film role, in Noël Coward's In Which We Serve, was in 1942, and the following year he had a successful run in the stage version of the film that would make him a star, Brighton Rock. In between, he spent the final two years of the war in the RAF, pausing briefly to marry Sheila in 1945.

Her stage career began with Ivor Novello's Fresh Fields in 1942 at the Intimate Theatre, Palmers Green, and included working at the pioneering little Q Theatre in Kew, being directed by Gielgud in the melodrama Landslide (Westminster, 1943), and starring in the jocular 1066 And All That (Palace, 1945), School for Spinsters (Criterion Theatre, 1947), Love's a Funny Thing (Ambassadors Theatre, 1949) and To Dorothy a Son (1950) and Double Image (1956) at the Savoy Theatre. She also reunited with Gielgud to play the goddess Iris to his Prospero in The Tempest (Theatre Royal, 1948).

Her film debut was a high-profile one, as one of the three leads in Michael Powell and Emeric Pressburger's strange and beautiful love letter to the English landscape, A Canterbury Tale (1944), a reimagining of Chaucer that bewildered critics upon its release but which is now considered one of the pair's most rewarding works. Sim played a land girl, one of three modern-day pilgrims; fittingly, she had herself served in the Women's Land Army in Hereford during the war.

For all the tally-ho-ing and morale-boosting of British cinema in the 1940s, many of the films were a great deal more interesting than they were required to be. Great Day (1945) was ostensibly a home fires burning story of the women of a village preparing for a wartime visit from Eleanor Roosevelt, but the film's real interest is in the human dramas, including Sim's character caught in a love triangle and her father (Eric Portman) caught in circle of disillusionment, nostalgia and heavy-drinking.

Her first film alongside her husband was Dancing with Crime (1947), the story of a cabbie driven by the death of a friend to expose a gang of crooks, in which she and Attenborough, wrote one critic, "made a pretty pair of babes in the Soho-cum-Camberwell wood".

The Boulting Brothers fable-like The Guinea Pig (1947) cast the 25-year-old Attenborough convincingly as a 14-year-old schoolboy from a working-class background who wins a scholarship to a public school only to find his hard work has led him into a life of misery and bullying. Sim, as the headmaster's disarming daughter, is the one bright light in the gloomy world, the film's occasional sentimentality held at bay by Attenborough's moving performance and Sim's gracious one. Sim was then signed by J Arthur Rank, and made further appearances alongside her husband in The Magic Box (1951), alongside James Mason in Pandora and The Flying Dutchman (1951) and finally in The Night My Number Came Up (1955).

The couple appeared regularly together on radio in the early 1950s, pairing up for a serialisation of Agatha Christie's Partners in Crime (1951). At the same time, they were both in the West End, making history in the London premiere of The Mousetrap, in which Attenborough originated the role of Detective Sergeant Trotter and Sim that of Mollie Ralston, owner of the Monkswell Manor guest house. The play had its world premiere at the Theatre Royal, Nottingham, before moving to the West End and never leaving; on Tuesday evening the performance at St Martin's Theatre was preceded by an announcement of Sim's death.

In later years Sim served as a magistrate and was heavily involved in charity work and in restoration and conservation work in Richmond, which was home to the family for many years. She served on the Actors' Charitable trust for six decades and was a Trustee of Denville Hall. Despite the long lives Lord and Lady Attenborough enjoyed, the deaths of their daughter Jane and granddaughter Lucy in the 2004 tsunami in Thailand were doubtless contributory factors in the decline of a truly inspirational partnership.

Sheila Beryl Grant Sim, Lady Attenborough, actress: born Liverpool 5 June 1922; married 1945 Richard Attenborough (died 2014; one daughter, one son, and one daughter deceased); died Denville Hall, Middlesex 19 January 2016.