Paul Theroux came on stage at the Lyttleton Theatre on the South Bank to loud applause. He then started ruffling papers and reading quotes from negative reviews. Turning to the audience he said, "You must have all read these . . ."

"Yes," we replied in unison.

"No you haven't," Theroux responded. "These are reviews of Boswell's Life of Samuel Johnson."

There were embarrassed titters in the audience. From then on, we were putty in Theroux's hands as he spoke engagingly about his book In Sir Vidia's Shadow which chronicles the end of his 30-year friendship with V S Naipaul. When we got to questions, it was obvious that most of the audience were au fait with the much-publicised literary feud because they kept asking knowing questions about Naipaul's snobbery, racism, misogyny and general cantankerousness.

We all enjoyed the debunking of a great figure as Theroux held forth. I could sense the deep pleasure many must have felt in hearing that the man often referred to as the greatest living writer in English and the one writer who has dissected the corruption of the emerging societies is also a heartless, prejudiced, woman-hating miser. How could such a man have kept any friends?

The truth is that he is undoubtedly an immensely talented writer. And the private doings of a writer such as Naipaul - who draws a lot from his own life - is certainly of some interest. But must we not draw a clear line between the two? Has Arthur Koestler's much-discussed satyriasis added to or detracted from the merits of Darkness at Noon? There are countless writers and artists who were unbearable in private, but came up with sensitive, thoughtful works. As Naipaul has said on several occasions, the work must precede the man. By dwelling so much on his foibles, we might lose our focus on his impressive body of work. It is time we started making a distinction between the message and the messenger.

I admit to being an avid admirer of Naipaul, whom I first read in Africa when I was 18. I was then in Lubumbashi, in southern Zaire, and a Zairean academic had given me a copy of his essays on Argentina and the Congo. Those were the days when the late Field Marshal Mobutu used to come on television to deliver day-long speeches about the need to return to African roots. Mobutu was then syphoning his country's fortunes to banks in Switzerland, Austria and Portugal. Naipaul, who had been in the Congo soon after Mobutu came to power, had seen through the facade of his project. In Finding the Centre, a collection of journalism, there is an essay entitled "The Crocodiles of Yamousoukro", in which Naipaul reflects on how, in his quest for glory, the then Ivoirian president, Houphouet-Boigny, was trying to transform his home village into a metropolis. This essay was written many years before Boigny built one of the largest cathedrals in the world, an enterprise which - in such a poor country - had embarrassed the Pope.

Naipaul's writing on Africa now seems prophetic. A Bend in the River remains one of the most perceptive novels about the disintegration of post-colonial Africa. Naipaul has also written incisively on a condition that is increasingly common - dislocation. Here is a man who has taken the vocation of writing seriously, and he remains a model for many aspiring writers.

Some of Naipaul's public utterances are often extreme and ill-judged. Perhaps people ought not to take him so seriously because his many contradictions are a striking feature of his personality. Here is a man who thinks that no writing of value can come out of Africa. Yet I know of a Nigerian writer who wrote a perceptive book about his country, which he sent to Naipaul hoping for some reaction. Naipaul invited him to his house and went through the book sentence by sentence. For a while this writer would not have a bad word said about Naipaul.

I once interviewed Naipaul for the magazine section of a Lisbon weekly. I met him in his scrupulously clean flat in Kensington. When I told him I was from Angola, he asked about my native language and how far it would take me. He then asked after my family, and what I thought of life in England. When he realised that I had read most of his books, Naipaul warmed to me further and started giving advice on writing. I felt deeply privileged to be in the company of such a highly intelligent man. From the stories I had heard of him, I had been expecting an aggressive, irascible figure. Instead, we were now having a congenial tete-a-tete. Naipaul told me he had just been banned from driving (he had been driving on the wrong side of the road) and delighted in telling me which bus I needed to take home from his neighbourhood. At some point, I had even begun to worry that my editors in Lisbon would not believe the author famed for his temper was not acting to form.

Then I quoted C L R James, the late Trinidadian writer who once said that white people liked Naipaul because he said what they wanted to hear. Abruptly, Naipaul's West Indian accent stood out as he began shouting at me. Suddenly I became terrified of the great man before me. I would not relish the idea of meeting him again, yet I remain an ardent admirer of his craft, vision and dedication to the writer's life.