It is seven o'clock on Friday night in Victoria, London. Commuters are pouring into the station, bound for a quiet weekend on the Sussex coast. Standing out from the suits are a large group of twentysomethings, lounging beside a dishevelled pile of backpacks and string bags. These are the weekend's takers for the Can-A-Bus, a fortnightly coach service run by the tour operator Wicked Travel, bound for three days in Amsterdam.

'I dunno what Amsterdam's like, but I don't care,' says Vicky, 22, who has arrived with 12 friends from Oxfordshire. 'I just know about the drugs, and the red-light district.' From its appearance, the Oxford group has decided to get into the spirit of the 'Dam several hours before boarding the bus. 'Yeah] We're all Amsterdam virgins,' shouts her friend Danny. 'I don't even like dope very much,' says Marc. 'But I just want to get into a public place and smoke openly. You have to do it. What am I expecting from the trip? Memory loss, that's what.'

Wicked Travel was launched in December 1993 by Belfast-born Jim McCabe. Mr McCabe, now in his forties, discovered the delights of the Amsterdam cannabis (hence Can-A-Bus) scene a mere nine months ago. He is an enthusiast, operating his travel service with missionary zeal. 'Roll up] Roll up] For the Can-A-Bus]', he shouts hoarsely as we climb aboard. In case we haven't yet quite got the idea, a large sandwich board, adorned with a giant marijuana leaf, stands beside the doorway.

'Basically, people come on the trip to take drugs,' says Brendan McKavanagh, the Can-A-Bus co- organiser. 'That's purely it. And if they want dope, ecstasy, or coke, then we point them in the right direction, so they know they're getting good stuff. I think we're a necessary service.'

The brochure also promises 'tours around the red-light district', 'the best quality goods anywhere in The World' and meetings with 'local contacts to ensure you aren't ripped off'.

There are 50 of us aboard; most of the group, who have each paid pounds 79.95 for the two-night trip, are young professionals under 25. There are no students, although a large majority still live with their parents, who appear to have no idea where their offspring have gone. 'They think I've gone to Paris,' says Billy, one of the Oxford group. 'Ha Ha Ha]'

'My employers think I've gone on a driving holiday around France,' says Hayley, a 24-year- old nanny from Knightsbridge.

McCabe's conviction that the delights of Amsterdam need to be introduced to the public seems to be a canny one: most of the people on the bus had never been there before. McCabe is planning other themed trips to the 'Dam, including 'Erotic Breaks', gay and lesbian weekends and 'Horny Holidays' where, if you want three-in-a bed, or any other such combination, it will be provided.

Meanwhile, spirits on the bus are high, even though we have only got as far as World of Leather in Eltham when the on-board lavatory packs up. 'It's gonna be an eye-opener,' says 22-year-old Warren from Hornchurch in Essex, who is on the bus with his mates Tristan and Gavin.

We arrive in Dover and pull up alongside a coach-load of cubs, who peer in excitedly. In the Can-A-Bus people are running up and down the aisle, waving cans of beer. McCabe wanders around saying 'No tulips] No windmills] No boredom]' in a thick Belfast brogue.

We are not due to arrive in the 'Dam until 6.30am; however, McCabe keeps spirits aloft throughout the night by intermittently grabbing the on-board microphone and intoning hoarsely, 'We're now in France . . . We're all going to the Dam] . . . Here we go,' and so on. As we approach Holland the excitement is palpable. 'I just wanna smoke some hooch, man,' says Clint, from New Zealand.

As far as the good citizens of Amsterdam are concerned, visits by the likes of the Can-A-Bus crowd, who each carry up to pounds 500 in cash, are manna from heaven. 'The English drink far too much and they smoke too much,' says Pieter, manager of the 1,600-seater Grasshopper bar in central Amsterdam. 'More than any other of the Europeans. They get very excited and then they pass out. Travel reps all carry glucose so they can wake them up. Every weekend we have two keel-overs; English people don't care how uncool they look. If they didn't come over, we'd all go bankrupt.'

Now that Germany has legalised cannabis, are the Dutch worried that the same might happen in Britain, where doctors have begun murmuring about its beneficial qualities? 'Never,' says Pieter. 'England is too old. It will never legalise drugs.'

The excitement of doing something that is illegal at home is, clearly, the thrill of taking the Can-A-Bus tour. The coffee shops, which also sell dope, open at 7am. By 7.15am, McCabe, singing 'Go Go Go Go] Esso Blue]', has led his fellow travellers into La Rocka (one of the largest), where they quaff beer, queue up at the counter to buy grass and roll joints. By 7.50am, most of the Oxford group have collapsed over their backpacks.

They sleep until about 10am, when they will get up, check into their hotel (shared rooms in a glorified youth hostel), and then fall back into the bars. Much of the remaining time is spent in a particularly seedy one called The Frisco, where Scottish football supporters, on a similar voyage of discovery, are aiming to drink the place dry. One man causes a minor scandal by taking all his clothes off.

Meanwhile, the trio from Hornchurch sit in La Rocka holding their joints somewhat self-consciously. One of their group, Gavin, has gone missing. After about 20 minutes, he returns from the gents looking grey. His friends shake with laughter: Gavin, no expert at serious dope- smoking, has badly overdone it. He looks at them, palely unrepentant. 'I don't care. It's what I'm here for.'

(Photographs omitted)