Simone de Beauvoir was certainly not a wreck after Jean-Paul Sartre died in April 1980. But for the next six years, until her own end in 1986, she was a terribly lonely soul. The decade of the 1980s, in more ways than one, was fundamentally the end of an era, one that Beauvoir and Sartre had both epitomised for years together. They were academics who loved a good, spirited debate between themselves and with their friends. They frequented bars and restaurants, spent time reflecting on the vagaries of life and sat for hours writing and watching the world go by. Existentialism, they believed, was all. The mundane, well, it did not appeal to them much.

But that is the not the beginning and end of the Beauvoir-Sartre relationship. There was a whole lot more. From early on, indeed from the time they met in their twenties, the two individuals were drawn to each other in ways that remain inexplicable even by the standards of the twenty first century. It was more than a moth-drawn-to-the-flame story. Who was the moth? And who the flame? Sartre was impressed by the furious intellect at work in Beauvoir, who in turn quickly came round to the conclusion that she needed to ditch her boyfriend and link up with Sartre because of the powerful mind at work in him. From there onward, it was sex that soon took over.

The physical relationship that the two shared was one of overriding passion, proof that the libido was what mattered to them most. That was not surprising. But surprise was to come along soon, through Beauvoir and Sartre reaching a deal that would allow them room for intimate relationships with others they came in touch with. And they surely did develop likes and strong attachments for men and women (in Sartre's case it was usually a bevy of young women who made their way to his bed) down the years. Amazingly enough, they never felt there was any reason to let all those relationships, some of them quite peripheral to the love they had between themselves, come in the way of their scholarly attitude to life. He called her his little Beaver. She constantly worried over his health when he was away from her.

Like Abelard and Heloise, as Hazel Rowley points out at the very beginning of this unputdownable work, 'they are buried in a joint grave, their names linked for eternity'. But eternity in terms of the contributions Beauvoir and Sartre made to academic life, indeed philosophy, remains on a grander scale. Both produced volumes of work that remain hugely remarkable not only for their sheer amount but also for their intensity. There were all the philosophical essays and the plays, the novels and the travel narratives, biographies, memoirs, et al, that they produced over a fairly long stretch of time, almost till the end. Through the governing passion of their love for each other, through their search for physical gratification in other women and men, they did not cease to be writers. Indeed, it was the raw need for the pleasures of the flesh that often seemed to push them toward greater heights of intellectual creativity.

And what impact did their love for each other have on all those others whose lives they entered at some point? The American Nelson Algren, for one, fell in love passionately with Simone de Beauvoir, and she with him, before matters took on a bitter hue with Beauvoir writing about the relationship in not so flattering terms about Algren. For his part, Sartre went through a series of relationships, one of the most intense being with Olga Kosakiewicz. He soon followed it up with her sister. There were the others, like Evelyne Lanzmann, who killed herself in November 1966. Sartre's clandestine affair with her had gone on even as he kept himself sexually involved with Michelle Vian. And then there were, of course, the lesbian relationships Beauvoir felt drawn to, with young women like Sylvie Le Bon. As Le Bon was to note years later, she and Beauvoir were intimate, their relationship 'carnal but not sexual'.

For almost the entirety of their careers, both Sartre and Beauvoir believed intensely in the power of politics to save the world. To be sure, Sartre's commitment to politics was a whit more involved than Beauvoir's, but what united them in outlook was their feeling that too much of hypocrisy and an abundance of inhumanity came in the way of the making of a happier world. Which is probably why Sartre was not terribly impressed, let alone cheered, when news of the Nobel Prize for literature being awarded to him, in 1964, came along. He would not accept it; and he did not. The writer, Sartre (and with him Beauvoir) believed, did not need to be a celebrity.

But the writer of necessity had to be associated with all those causes that affected the human condition. In the late 1940s, Sartre made his first trip to the United States. He came away unimpressed. By the early 1950s, he would make the first of quite a few trips to the Soviet Union, get drawn to what he thought was a huge enterprise poised to change the world. His infatuation with the Soviet Union would last a long time, until one morning he thought he was seeing things he had not observed before. But by that time he had already incurred the displeasure of other writers, those who had noted Sartre's earlier reluctance to condemn the Moscow authorities for the degrading treatment of their intellectuals.

Rowley stitches together a fine tale here, through an inter-weaving of the ways the minds in Sartre and Beauvoir worked. The world has, without ambiguity, always known about the depths which they both plumbed in order to assert their relationship over and over again. What Rowley does differently is to give the two lovers a life that applies to them both, that brings them to life, as it were, in the form of a single whole rather than two disparate entities.

On the morning of Sartre's death, Beauvoir lay beside his corpse, on top of the sheet that covered him and concealed his gangrenous bedsores. On the day of the funeral, as the undertakers prepared to close the coffin, she kissed him on the lips to say goodbye. In the days following the burial, Beauvoir fell ill; but once she began getting back her strength, she sat down to write the moving Adieux: A Farewell to Sartre. She began thus: "This is the first of my books --- the only one no doubt --- that you will not have read before it is printed."

In April 1986, five thousand mourners followed the hearse carrying Simone de Beauvoir's coffin down the streets of Montparnasse. Her ashes were placed in the grave that contained Sartre's.

The article is based on a reading of Hazel Rowley's Tete-aTete: The Lives and Loves of Simone de Beauvoir and Jean-Paul Sartre, a Chatto and Windus publication.