Smash hit

Jacquetta found married life smothering. "In all things social and intellectual it was admirably balanced and free... also becoming every year more lifeless and stultifying. If we had known real passion together, everything else might have been well." In 1935, Christopher suffered a near-breakdown. Overwork was said to be the cause, and Jacquetta sought refuge in archeology.

They had one child, Nicolas. As a mother during the second world war, she was evacuated to Dorset, where she experienced "a passion for a woman that told me what it would be like to be an adolescent boy. My body was only mildly interested if at all". Unnerved by her unusual interpretation of the concept of courtly love, she fled back to London, at the height of the Blitz.

In 1946 she met the brilliant Australian poet Walter Turner, her senior by some years. His letters to her suggest that the affair they went on to enjoy turned out to be the heart-and-body romance she had been searching for. They consummated their affair in grabbed moments of high passion. Turner had other lovers, but Jacquetta was deeply in love with him, so much so that when she bumped into him unexpectedly at a London gallery, she promptly fainted.

In November 1946, Turner died suddenly of a brain haemorrhage. Jacquetta was devastated. She and Christopher were still very much a couple to the outside world, though he was spending much of his time at Oxford as professor of European archeology. Christopher knew about his wife's liaison with Turner, but such was her grief — and the depth of his love for her — that he wrote her a letter of condolence, which has also found its way into the archive. "My darling I feel your grief for Walter's death inexpressibly much and do assure you of my very deepest sympathy. It is a dreadful shock and sorrow and loss to you which I know is irreparable. Loneliness I feel sure is what you feel worst, and a sense of being cut off from a vitality and happiness."

But within a year Jacquetta had met J B Priestley. It was early 1947. Jacquetta was a newly appointed Unesco secretary for the UK, and Jack Priestley was among the delegates at its inaugural conference in Mexico City. Jack and Jacquetta. Anima and animus. A neat pairing of male and female which belied a conventional love match. Jack, a married, overweight, blunt Yorkshireman; Jacquetta, 15 years younger, sleekly presented, the daughter of a Cambridge don. Few could understand this urgent attraction, but Jack plainly adored her. Forthright and unyielding to his public, in private he lived in thrall of his "honey of a girl" whom he called his "dearest Puss".

The romance began with dessert. A noxious-looking pink jelly offered to Jack by a woman with a certain smile whose signature alone had intrigued him for weeks — "J J Hawkes", Mrs Jacquetta Hawkes, author, archeologist, wife of a distinguished professor. "Very few words were spoken," Jacquetta recalled of that "Moment of the Pink Cake" as they always referred to it, "yet we were to feel all was decided from that moment". Meanwhile, Jack had already given his verdict to a friend: "What a woman — ice without and fire within!"

In a hotel room in Mexico, Jacquetta found "the pleasures and spiritual transformations of total love . . . Jack, I believe, took an added delight in his secret knowledge that my outward appearance of excessive coolness was now no more than a deception".

But there was another deception. Jacquetta recognised the cost of this "union of body, heart and mind". It was a relationship that, she said, "could certainly be called disreputable and in our existing circumstances even deplorable".

But she was not about to give it up. Jacquetta's enthusiasm for her total abandon with Jack came partly from a desire to express herself and from the fact that she was entombed in a failing marriage. She said she revelled in the wildness of those days, and that "to be such a mistress was a finer thing than to be a wife". Jack told a friend, the writer John Braine, that before he met her "I was always looking for something". But according to Jacquetta, it was Jack who was dissatisfied with their meetings and the fact that they were almost exclusively based on lovemaking.

When they met, Jack had already achieved fame as a wartime broadcaster, playwright and social commentator. Jacquetta was also well established: she was part of a circle of left-leaning post-war, post-Bloomsbury actors, artists, writers and thinkers that included Henry Moore, Laurie Lee, Ben Nicholson, Robert Graves, Ralph Richardson, Herbert Read, Iris Murdoch and Laurens van der Post. This mix of arts and science was very Jacquetta. Over the years the circle talked, fell out, made up, wrote postcards and long letters. They inspired each other to challenge norms and defy convention.

Although Jacquetta had begun to make a name for herself with Christopher, it was not until she met Jack that she really flourished. They were a popular couple with an exclusive address: Jack's rooms in Albany, Piccadilly.

After their initial tryst in Mexico, Jack left Jacquetta to return to Britain, where his domestic life was troubling him. His daughter, Mary, had emotional problems and he was beset with guilt. On a train to New York he poured his heart out to Jacquetta, writing on the notepaper of the Hotel Maria-Cristina: "I know I shouldn't be doing this — it's against everything I meant or even said. I had opened my bottle of Scotch and was sipping and staring and brooding when you came flooding back to me in full and terrible force and then ever since it has been hell. Missing and missing and missing you." Jacquetta wandered around Mexico City trying to send a telegram to Jack saying she felt the same.