So how did a nice Jewish boy from Brooklyn come to make a film about Edward Said? In November 1974, when Yasser Arafat came to New York to speak at the United Nations, I was a freshman at Columbia. While Arafat, dressed in keffiyeh and fatigues, told the General Assembly, "I have come bearing an olive branch and a freedom fighter's gun. Do not let the olive branch fall from my hand," on the sidewalks outside, a crowd of demonstrators, most of them Jewish, chanted: "Arafat, go home." I was in that crowd.

Two years later I was still at university. I was interested in the overlap between philosophy and literary criticism and wanted to go and see Roland Barthes in Paris. (I also wanted to loaf in cafes, drink endless grandes cremes and generally make the most of being 19 years old and abroad.) But I was broke.

My adviser suggested my grant application would be much more successful if it was endorsed by his friend Edward Said, at the time the only tenured member of Columbia's English department on speaking terms with French theory. All I knew about Said was that he was a Conrad scholar and the author of Beginnings, a book I was struggling to read. When I met Said in his office he quickly divined that my interest in structuralist theory was, well, rather theoretical. Far from being shocked, he seemed amused, and agreed to sponsor my research.

"How did you come to be interested in Barthes," he asked, "and what is your family background?" As I didn't have a good answer to the first question, I answered the second. "My father," I said with what I thought was great wit, "runs the Reading, Pennsylvania branch of the International Zionist Conspiracy." At the time, my father was the director of the Jewish Welfare Federation of Reading and spent most of his days raising money for Israel. Said gave me an odd look but said nothing. And off I went to Paris. When I returned to New York the following year I wrote up my research on Barthes for Said, who gave me an A, explaining that "as an intellectual, you have an obligation to the truth even when it doesn't fit your preconceptions", and that by this measure my work had room for improvement.

Orientalism, a book that changed the way we read culture - our own and that of "others" - was still a year in the future. At the time, it was possible to be ignorant of Said's membership of the Palestine National Council - indeed, of his very identity as an Arab - even for those more observant than me. What was unmistakable about him was his generosity, his seriousness and his sense of responsibility: "you have an obligation".

I don't know whether it is true to say we ever became close friends. In my senior year Said and his friend Michael Rosenthal (my adviser) taught a seminar together on European novels. One of the books we read was Giuseppe di Lampedusa's The Leopard, a novel shot through with nostalgia for Sicily's vanished aristocratic order. Outraged at being forced to take this egregious piece of elitist self-pity seriously, I wondered whether the assignment was a kind of a joke - an example of reactionary fiction. It took me years to understand why Lampedusa's evocation of loss spoke so strongly to Said. I think the first conversation we had about literature that did not turn into an argument was when I came back from graduate study in England. What had I been reading? he asked. "A lot of Henry James," I replied. He nodded non-committally. And Thomas Carlyle. I had just written an essay on Carlyle and John Ruskin. Said stopped walking. "Carlyle. I hate that fucker," he said, launching into a mini-tirade.

I saw Said only intermittently over the next several years. But we often spoke on the phone, which in his hands was a virtuoso instrument. His appetite for gossip and scandal, particularly among the literati, was enormous. During these years he also became the west's most visible Palestinian. He started writing music criticism for the Nation. When we lived in Brooklyn my wife and I would occasionally meet Edward and his wife Mariam at the Brooklyn Academy of Music, or walking afterwards down Atlantic Avenue for a late supper at the Tripoli, an Arab restaurant.You had only to see the way all the staff, from the maitre d' to the dishwashers, came over to greet him to get a sense of what he meant to the world outside the US.

We hardly ever talked about politics. I remember getting an invitation to a breakfast he was organising for Arafat and thinking that I would probably go - although in the end the State Department refused to grant the PLO chairman a visa. Ironically, it was not long afterward that we had our last real argument, over the Oslo Accord, which filled me with hope but which Edward condemned as a betrayal of Palestinian aspirations that was doomed to fail. I don't think he took much pleasure in being proved right.

The news that Edward had been diagnosed with leukaemia was devastating, but then he just carried on, and demanded that you carry on, and so you did. Once when I went to visit just after he had returned from a round of chemotherapy, he looked drained. But the next time I saw him he seemed miraculously restored. I began to believe that even if his cancer was incurable, Edward would wrestle it to a standstill.

So I was shocked, and worried, when he told me in the summer of 2002 that his immune system had collapsed. The worst part, he said, was how cut off he felt. He couldn't go anywhere. He couldn't see anyone. That was when I suggested taping a series of interviews. The idea, at least on the surface, was to produce a kind of proxy, so that if he had to cancel a speech at the last minute for health reasons, he could send along the tape instead. But it would also be a chance to say what he wanted about the topics that mattered most - his work as a critic, his love of music, his childhood and, always, Palestine - without having to be tied down by any specific occasion or audience.

When Edward said he would like to do it I asked Charles Glass, a mutual friend and reporter for ABC News, if he would ask the questions. We filmed in Cambridge, in November 2002, over a period of three days. For me, those days were a great gift. Mike Dibb, who directed, had worked with Edward years earlier, and the atmosphere he created on set resulted in a portrait of extraordinary intimacy. It is a very spare film: no tricks, no gimmicks, no cutaways - just incandescent conversation. We recorded six hours and edited it down to slightly less than two.

When we were first roughing out what we wanted to cover I came across a passage in Beginnings on the tricky business of interviewing writers, who can, after all, speak for themselves in their work. "The only sort of interview that one could, if forced to, defend would be where the author is asked to articulate what he cannot write." That passage, which turned out to be a quotation from Roland Barthes, and which so completely sums up what we were trying to do, now sits at the beginning of the film we made.

Did we succeed? You'll have to see it for yourself to decide.

Edward Said: the last interview is showing until 22 July at the Institute of Contemporary Arts, The Mall, London SW1 (020 7930 3647)

D D Guttenplan is London correspondent for the Nation