For well-nigh half a century, John Berger - poet, essayist, critic, novelist, playwright, veteran guru of the left - has taught us new ways of thinking, new ways of seeing the world. So what is he doing now? Drawing motorbikes. He tells Andrew Lambirth the reason why.

A compact, energetic figure with white hair, John Berger will be 72 this year. He was born in Stoke Newington, North London, but for 30 years he has lived abroad, and now makes his home in a village in the French Alps. He is hesitant in conversation; you feel that he is weighing every word, searching for the mot juste. There is the parallel sensation that he is translating from another language - French? - as he speaks. At one point he says: "freedom, but not with a capital L" (as, presumably, in Liberte), before quickly correcting himself. His "no" reverts to a "non" at times of emphasis.

His apparent shyness is no doubt a mask for his sensitivity - the sensitivity that permits him to respond so intricately to works of art, people and places. His seriousness is matched by a willing sense of humour; Berger has a warm presence; he is charming and courteous. Yet there is also a reserve: you sense a hidden, private core to the man, which may or may not be serene.

Today, John Berger is perhaps best known as a Booker Prize-winning writer of fiction, yet even those whose eyes were opened by his extraordinary 1972 TV series, Ways of Seeing, may not be aware that he began life as an artist, training first at the Central School, where he stayed for almost two years before going into the army. Demobbed in 1946, he continued his interrupted education at Chelsea School of Art. There were good teachers on the staff: Robert Medley, Geri Richards, Henry Moore, Julian Trevelyan. At that point Berger saw himself as pursuing a life in art.

He had some success in group exhibitions, then in 1953 he was given a solo show at Wildenstein's of some 15 or 20 paintings, nearly all of which are now dispersed to the winds. The Wildenstein show was his last in England until this week. He returns now to the gallery circuit with 14 recent drawings, showing at Purdy Hicks, near the new Tate at Bankside. A modest show, but full of interest, and highly typical of the man.

I am interviewing him in the gallery, and we return to the story of his development. What does he think now of the paintings of that early period? He frowns. "Several things. First of all, that they are often quite clumsy. And then, almost the opposite: that they could be freer, that they're a bit constipated. But I can also see in them, somewhere struggling behind that restrictiveness, a kind of passion, which I can recognise perhaps as mine."

It was in 1953, too, that Berger stopped practising as an artist. Not that he stopped drawing altogether, but being an artist now took second place to writing, and drawing became simply an activity he undertook from time to time. "Like a diary?" I ask. "No, it was either more functional than that, or more relational. Either I drew because I saw something and wanted to remember it for some quite definite purpose, or I would draw something which I thought would help me with my writing. Sometimes I would draw portraits of people I was inventing in a book, or portraits of intimate friends. I've always done that - it's not really a question of making a portrait but of trying to follow the traces of their lives, which are somehow visible in their hands or in their faces."

Despite, or perhaps because of, his need for precision of expression, Berger notoriously finds writing difficult, and turns to drawing almost for light relief. He makes no big claims for his new exhibition, but he's always been keen to put on record the various aspects of his creativity - whether essays, criticism, plays, poetry, photographs or fiction. The drawings, mostly in charcoal or ink, are clearly important to him, but he remains modest about them. "About four or five years ago, I began to draw more and more. And then I realised something. For 35 or 40 years, I really wasn't drawing very much. One would suppose that, if one then went back to it, one would more or less go back to where one had stopped. But I found surprisingly that, during those mute years, things had gone on developing, there had been an evolution. So I was actually further on."

So why did he give up art for literature? "The creative choices that one makes in a life are much more incoherent and compulsive than one pretends afterwards. It wasn't really because I became discouraged about myself as a painter. No. Of course I had days of despair, as everybody does, but that hadn't overburdened me. It was the height of the Cold War - 1952, '53, '54 - we were living under the imminent threat of nuclear war. It seemed that one really had to protest in order to make this terminal catastrophe even slightly less likely. In that situation, to draw and paint seemed not urgent enough. Of course, one could have made posters and agitprop, but it's not something I ever did.

"I had a certain capacity to write. I discovered that when I was a kid at school. I wrote poems, letters... It became possible for me to become a journalist, and I could talk directly about the nuclear threat and the political choices. So it was a kind of urgent, somewhat desperate politicisation which led me to begin writing. Having done that I began to see that it was difficult to combine these two activities. Painting has to be a full-time activity. You really have to be covered with this material that you're working with, whether it's paint or clay. So I then decided that, rather than be a one-handed painter, it was better to stop."

Berger was the feared and respected art critic of The New Statesman for a decade (1952-62), writing in favour of social (not socialist) realism, a logical extension of his commitment to Marxism. He also wrote other journalism, but it was not long before he felt the urge to go beyond reporting the immediate, and explore fiction. His first novel, A Painter of Our Time, published in 1958, is primarily about painting. The book has an experimental and slightly didactic feeling to it, and is based on a group of people, many of them emigres from Central and Eastern Europe, who lived in the Finchley Road area. Berger says that if anyone inspired the observations on painting in the book it was a Dutch artist and close friend, Friso Ten Holt, who in fact died the week before our interview. Ten Holt also had a motorbike, a BSA, and made a number of journeys by bike with Berger. This is not as irrelevant as it sounds; from an early age, Berger has been passionate about motorbikes, and still rides one. Three of the drawings in this exhibition are about the experience of biking.

It is a subject Berger is convinced he will return to. "This is really just the beginning," he says. Two drawings feature a biker traversing a printed map. I ask whether this is Berger in conceptual mode. "They're not drawings about motorbikes, they're about the experience of riding a bike. I was working on the series, fiddling around, when suddenly I had the idea of drawing on a map. Then I began to see something which is not so much conceptual as phenomenological, to do with experience. The contours on a map, the rivers, the roads, the mountain ranges, begin to make a metaphor with the body of the motorbiker and the bike. In a strange way you become the journey that you've made, until the next one. You eat it and you shit it too; it passes through you."

We look together at other drawings in the gallery. One, O Betanzos, depicts a small town in Galicia, northern Spain. "It was a very poor town, from which thousands of emigrants left for Cuba and Latin America... I went there several summers; I love this place. I did several drawings, always with this obsession that Betanzos was a town which people left, so the drawing is about memory."

A triptych called Face Writing, done in ink on the pages of a Chinese notebook of absorbent paper, is a series of three self-portrait heads drawn with spidery economy. "With images of faces, what one looks for is to make that face also a place, a specific place." He means, in terms of where it was drawn - Inch Kenneth, in the Hebrides. And that's all the information that Berger thinks necessary to impart.

As visitors to his exhibition, our primary job is to look, not to sniff out autobiography. There are drawings of fish, made partly from Berger's interest in movement. Their particular appeal? "I suppose it is the fantastic intricacy of these creatures

`Drawings by John Berger' is at Purdy Hicks, 65 Hopton Street, London SEI (0171-401 9229) until 31 January. `Pages of the Wound', a limited edition of Berger's selected poems, photographs and drawings (John Christie at Circle Press, pounds 270), is on sale at the gallery.