The Hollywood look-alikes in the Katsu coffee-shop were in agreement: one must already have serious mental problems to dream even of committing suicide after ingesting psychedelic or magic mushrooms.

“You’re giggling so much, how can you be depressed enough to kill yourself?” argues a Steve Buscemi clone, referring to last year’s suicide of a French teenager, Gaelle Caroff (17), who plunged to her death from the Nemo building, situated over the tunnel to Amsterdam north.

We are discussing the imminent ban on the production and sale of fresh magic mushrooms — which came into effect this week.

The suicide of Caroff, who was on a school trip to Amsterdam, appears to be instrumental in getting the new legislation pushed through. It is reported that Caroff had a history of psychological problems.

Mark, an Amsterdammer, who resembles a dehydrated cross between Woody Allen and Al Pacino, is nodding: “Besides, tourists don’t respect the ‘shrooms enough. They’re here mixing it with lots of alcohol and super strength skunk [marijuana] — it’s bound to have a bad effect on you. You’re bound to see evil,” he says.

Having just spent a pleasant afternoon wandering around nearby Vondel Park after sharing a batch of Colombian mushrooms (psilocybe cubensis colombian) with Spliff, the pet goldfish, I could only concur.

An unprecedented fascination with the shapes and colours of tree leaves turning ochre as winter approached meant we didn’t get too far into the park’s 45ha.

Having entered Vondel Park — named after 17th-century poet and dramatist Joost van den Vondel — in the south, near the Van Gogh museum, we didn’t make it all the way to Amsterdam’s Filmmuseum in the Vondel Park Pavillion.

An Italian Renaissance-style mansion built in 1881, it is situated to the north of the park and is the Dutch national centre for cinematography with more than 35 000 films dating back to 1898.

At times, sitting on a park bench, the atoms of a tree’s bark or one’s clothes appeared to break free from their regular bond and dance away from their usually sober shapes with delicious infidelity.

Questions about what the socially conformist eye sees, rather than panic, followed.

Although Spliff did find an errant terrier ignoring his exasperated master’s call to “heel” while attempting to mount the ducks in a nearby lake, she had no such luck with The Fish, Pablo Picasso’s 1965 sculpture, found in the park.

The only unnerving moments came when leaving the Vondel Park and heading for Katsu. With cyclists dictating the rules of engagement on Amsterdam’s roads and paths, attempting not to be overrun by the ubiquitous chicks-on-bikes felt the hardest part of the ‘shroom trip.

Coming from a city like Durban, where cyclists often complain of being persecuted (and sometimes intentionally run over), the paramount right of the cyclist is rather disconcerting for pedestrians perpetually unsure of where to walk.

This makes Amsterdam — for all its variety of bio, skunk and hashish — an unfriendly city for stoners intent on skinning up. Pedestrian paranoia is a horrible thing. And you’re usually awakened from a stoned reverie by an irritated bicycle bell seconds too late.

Back at Katsu, the wizened Mark, nicknamed Hout (wood), asserts that Amsterdam’s reputation for having a liberal attitude towards drugs and sex means tourists feel they have a licence “to get off their tits here”.

This after drawing on a vaporiser filled with Big Buddha Cheese for what seemed like an entire winter — the time it apparently took Van Gogh to paint The Potato Eaters.

But it is a valid point. By Thursday the city starts filling up with groups of British chavs seemingly intent on wreaking havoc during a stag weekend, more laidback Spanish stoners and loads of wide-eyed American pie.

Earlier that day, while en route to the Kokopelli (Conscious Dreams) smart shop on Warmoesstraat near the city’s red-light district to buy our cranial mash, we pass two Brits clutching beer cans and packages of mushrooms: “Oh fuck ’em and the focking warnings — they say that to everybody. Let’s get ’em down,” one said to the other.

We’d chosen the Colombian ‘shrooms, described as having a “strong visual effect” and being milder than the Philosopher’s Stone (psilocybe tampanesis: a truffle-like variety promising a chattier trip and less visuals) or the Ecuadorian mushrooms (psilocybe cubensis ecuadorian) which provide the “strongest visionary state of consciousness”. All were available at Kokopelli, two weeks before the ban.

Last Friday the smart-shop owners association, Vereniging Landelijk Overleg Smartshops (Vlos) legally challenged the ban in The Hague.

The challenge was rejected, but Vlos secretary Paul van Oyen said: “We will probably appeal in the case of the interim judgement of the high court judge.”

Van Oyen said the ban would have a “pretty tough” effect on smart shops as “more than 50% of their turnover is in magic mushrooms”. He said although the sector was small, employing a few hundred people, job losses were expected.

He also felt the clampdown on mushrooms was part of a broader “hardening” of government’s attitude because of “Christian fundamentalism and ideology”. The Christian Democratic Appeal holds power in Holland.

Between 500 000 and 1,5-million doses of paddos (the Dutch nickname for mushrooms, from the word paddastoel) were estimated to be sold annually in the Netherlands until the ban on December 1.

Amsterdam’s health services released a study in January, which found that of the 148 cases addressed by emergency services between 2004 and 2006, 134 involved foreigners. Britons formed the largest group of those.

Vlos, which has called for greater regulation of the sector rather than an outright ban — which it says will lead to mushrooms going underground, leading to less regulation of sale — asserts that this is a “very small number of incidents”.

“Moreover, these incidents cannot be traced back to the exclusive use of ‘shrooms. There has been no scientific investigation of such incidents nor has there been any toxicological examination,” it complained in a statement prior to the ban.

Although dried mushrooms are illegal in the Netherlands, fresh mushrooms were available until this week because it was impossible to ascertain the level of psilocybin, the psychoactive alkaloid in them.