When my wife was told she had won a free holiday, she was too dazzled by the prospect of sun to hesitate. She grew up in Jamaica. She hates English winters. The Canary Islands would be warm and bright in early spring.

She had been rung up and asked a long list of questions about our holiday habits and income. Three weeks later, a letter from a company called Club International informed her that she had won a holiday on Lanzarote. We would have to pay our air fares, but otherwise the firm wanted only to popularise its resort.

It seemed likely that some catch was involved, but we could not really see how we would lose more than the fares, although my wife agreed to a 'tour of the resort' as a condition of the holiday. We promised our friends that we would count each shellsuit on the beach and every lump of sewage bobbing in the surf and then swore to each other that we would love it, come what may.

For the first few days it was difficult to live up to this resolution. Lanzarote is a sterile place, blasted by volcanic eruptions; even the island's vines are grown in fields of black lava grains, each plant in a hollow scooped out by hand. In a week there, I saw only one wild animal: a lizard. Much of the sand on the tourist beaches has apparently been imported from the Sahara.

The Morro Mar resort was, as advertised, five minutes from the nearest beach - provided you drove. It was a journey of about 10 minutes on foot, across a wasteland where the money had obviously run out on some jerry-builder. Half-finished aerial walkways crossed a mixture of concrete and lava to a shopping mall of which only the bottom half was occupied. The island government has ensured that there are no high-rise buildings and no hoardings along the strip. Still, it was a dispiriting place.

Our apartment was like a cheap American motel, with mildewed patches on the ceiling of the sitting-room and bedroom, and a troubling damp patch on the floor of the bathroom.

But these were not huge drawbacks: with a cheap, rented car it was possible to get miles away into a landscape full of Sturm und Drang - and Germans. The north of the island was lovely and wild, with surf breaking on lava reefs below huge cliffs. At the extreme southern tip, reached over a few miles of tooth-rattling gravel road, there are a couple of delicious beaches. Between them are miles and miles of frozen violence: cone- shaped mountains with their tops ripped away, impenetrable plains with a choppy sea of black and yellow lava.

The villages of Haria, Ye, and Arrieta, in the north, are all pleasant. Our three- year-old daughter was enchanted by the performing parrots in the tropical garden at Guinate. But at last we could no longer postpone our tour of the resort.

By then we had a fair idea of what the tour would consist of, since the door to the staff room was usually left open in the deserted reception block. The walls were postered with mottoes: 'Today is the first day of the rest of your life', 'Always CLOSE the deal', and 'Remember what KISS means in timeshare.' (It means Keep It Simple, Stupid.)

In fact, much of our tour took place at a table in the cafeteria. We sat facing Julien, the salesman, ignoring the proffered chair beside him, and took turns to allow Rosamond, our daughter, to sit on our shoulders and join in the fun. Within 10 minutes of the opening pleasantries, Julien admitted that he was, in fact, selling an international network of timeshares. But, he said, one must not allow the negative perceptions of journalism to cloud the wonderful reality. Interval International, his company, offered holidays all over the world. 'Tell me,' he asked us confidently, 'where would you like to have a holiday?'

''Prague,' said Caroline, enthusiastically. His grin flickered, but he ploughed on, repeating the question to me.

'And not just Prague,' added Caroline in a helpful gush. 'The countryside in Slovakia.'

'Where would you like to go?' He kept his imploring gaze on me.

'Montana,' I said.

This early exchange knocked the stuffing out of him. He only tried to sell us a timeshare for another hour, and though this seemed a grotesque imposition at the time, I later found a script on the wall of the salesmen's room which set out a pitch that should last four hours, including a video, and would not mention the word 'timeshare' in the first hour.

With his script derailed, Julien started to fantasise compulsively, the way a frightened toad will sweat. First he said that he owned two freehold properties in London, one of them a house with garden just off the Portobello Road. (If this were true, he would hardly need to hustle timeshares in Lanzarote for a living.) He owned his own travel agency, he explained, darting me hurt and angry looks between phrases, as if it were my fault that he was saying these things. He also owned a river and a lake in France, where he went fishing. He really liked fishing.

Seeing that even this failed to make me see him as a brother, he tried journalism. Did I remember the massacre at Chatila? Well, he said, he had been able to take photographs there and sell them for great sums of money - because there was a timeshare in Israel he was able to use as a base. A bold tactic, this, to sell apartments on the grounds that they made a great base if you wanted to pay for a holiday by photographing corpses.

The walls of the show apartment were predominantly dark blue and white; there was a chunky carpet in violent colours, glass-topped tables with fluted brass legs, floral sofa coverings, a microwave, dishwasher, washing machine, and CD player. We were silent for some time after he showed us in.

Encouraged by this response, Julien started up again. It could all be ours, he said. We could move in that very night. For only pounds 15,000, we could stay in places of comparable luxury all around the world for the rest of our lives. He ushered us reverently into the bathroom, where there was a triangular bath in peach. Here he played his trump card: he pressed a button beside the taps and the bath started to heave sluggishly. See] It was really a Jacuzzi]

At our own modest flat, the man upstairs flushed his lavatory as we returned, giggling in triumph, and ours reacted with a prolonged and stertorous eructation, followed by a vigorous flow of fluid across the tiled floor, from a leak at the base of the pedestal. All this could have been ours for ever, for only pounds 6,000.

While we waited for the maintenance men, I did some arithmetic. We were in apartment 941, one of the cheapest. There were probably a thousand on this one resort. If the average price were pounds 8,000, then you could sell the lot for pounds 8m - and then you could do it again, 52 times over, once for each week of the year. No wonder it was worth the owners' while to offer free holidays, especially when the holidaymakers would almost all buy their food at resort prices, from resort shops. No wonder that the six kilometres of Puerto del Carmen were wall-to-wall timeshares. More than ever, we admired the government of the island for keeping their tourists so well under control.

On the last day, we drove off to the Papagayo beaches on the southern tip of the island. There was a fierce wind, so that you got sandblasted as well as sunburnt, but the swell was gentle. I hung in the clear blue water, swinging up and down, letting the timeshare wash away from me; then we drove through the volcanic landscape to the port of Arrieta.

In a restaurant I asked in sign language what the fish on the menu were; and the waitress brought three to the table to show me, their eyes still plump and shining from the sea. The one I chose was sunburn-red and spiny and, when fried, utterly delicious. Then we found a small beach with only three other people on it, and lolled in the sun and wind until it was time to return, hand over the rented car, and fill in the little form asking how we had enjoyed the timeshare resort - which I did with scrupulous and enjoyable honesty.

(Photograph omitted)