When Edna Healey, wife of the Labour politician Denis Healey, wrote her book Wives of Fame (1986), about three women married to men of genius, her preferred original title was I Didn't Know He Had a Wife. It is to her extraordinary credit and talent that, although she did not embark on her career as an author until middle life, her success ensured that this was not a phrase that anyone could have subsequently applied to her.
Edna, who has died of heart failure aged 92, worked as a teacher as a young woman and later lectured, often on Charles Dickens, for the Workers' Educational Association and the English-Speaking Union. It was Dickens's friendship with Angela Burdett-Coutts, the great Victorian philanthropist who had inherited the Coutts banking fortune, that partly inspired Edna's first biography, Lady Unknown, the Life of Angela Burdett-Coutts. That, and the fact that the Healey family had twice lived in houses in the Holly Lodge estate in Highgate, north London, in the beautiful grounds of her wealthy subject's former home.
It took her friend Pearl Binder (wife of the Labour lord chancellor Lord Elwyn-Jones) to make her promise as they sat together in the Central Lobby of the Palace of Westminster that she would take a synopsis of her idea for the biography to her first publisher. The book, published in 1978, was a bestseller. Her achievement was a matter of great delight and some astonishment on the part of her better-known husband. "I wondered if he would ever have known what I was if I had not written that book," Edna observed drily in a later book of memoirs, Part of the Pattern (2006). "He is always a more attentive reader than listener."
It was a truly affectionate observation. In nearly 65 years of a profoundly close and loving marriage, both spoke often of the depth of their mutual love, of their support for each other and of how the independence of their respective careers enabled them to give each other the space that they needed to succeed individually and grow and mature together. They had met at Oxford, where Edna had gone to St Hugh's College shortly before the second world war, as the first pupil of Bell's grammar school, in Coleford, Gloucestershire, to win a place at the university. She was hugely impressed with a lecture Denis gave about Picasso – "this young man who knew everything" – and he, more prosaically, called the beautiful young woman with pink cheeks "Tomato Face".
In 1940, shortly after Denis had joined the army, Edna went to teach in his home town, at Keighley girls' grammar school in West Yorkshire. Their courtship lasted for years because of the war and Denis's absence abroad, but whenever they could, they talked ceaselessly as they walked and cycled in the Dales. They married at Christmas 1945 and honeymooned in the loft of the barn belonging to a pub in Wharfdale. It was not the most romantic of nights. They had just blown out the candle when an old lady opened the trapdoor, offering to read them her poetry, and Denis had a boil on the base of his spine. He told everyone at breakfast that his coccyx was sore.
In recent years of relative retirement, her success as a writer, broadcaster and lecturer was relished by her husband, who readily acknowledged her superiority to him as a public speaker. She believed that the spoken word was more her medium than the written. "Somehow the thing that's in my head is never matched by what's on the paper," she once told this newspaper. "If only I could write what's in my head I might never have wanted to do anything else. But sometimes, it seems, I only really know what I think when I've heard what I've said."
She was encouraged to read by her father, Edward Edmunds, a crane driver, who warned her that she would be sent to work in the pin factory if she did not apply herself to her books. She was born, the fourth of five children of Edward and his music-loving wife Rose, nee Crook, at the close of the first world war in Coleford, on the edge of the Forest of Dean, not far from Newnham, where Denis's maternal grandfather was the stationmaster, signalman and ticket collector. Her childhood was profoundly happy, although her father died from pneumonia at the age of 46.
As the wife of a prominent politician, Edna was obliged to learn to deal with being ignored often. She gladly played the major part in raising the couple's three children, Jenny, Cressida and Tim, and learned to laugh about being invisible. She accepted that in the event of a political crisis, her husband's work would take precedence, but when he retired and they moved to their last home in four lovingly tended acres of the Sussex Downs, he spoke frequently about the joy of a life enriched by their love and in which there was no competition from the world of power. Their happiest time was walking to the top of the garden every day where, to the accompaniment of a drink and Mozart, they would tell each other how lucky they were.
When presented with a lifetime achievement award last year, Lord Healey, as Denis had become in 1992, told his audience that he wished to recite a few words written by Shakespeare about Edna, three centuries before she was born. He then read Sonnet XVIII, "Shall I compare thee to a summer's day", which ends: "So long as men can breathe, or eyes can see, So long lives this, and this gives life to thee."
Lady Healey also published Coutts and Co (1992, a history of the royal bank), The Queen's House: A History of Buckingham Palace (1997) and Emma Darwin (2001). She made two film documentaries, Mrs Livingstone, I Presume (1982) and One More River, the Life of Mary Slessor in Nigeria (1984). She is survived by her husband, three children and four grandchildren.
• Edna May Healey, writer, lecturer and film-maker, born 14 June 1918; died 21 July 2010