HELLO, I'm here, damned, at the Edinburgh Festival Fringe, the largest arts festival in the world. It's called the "fringe" because it happens at the fringe of civilisation, the fringe of sanity. I live the word fringe. Fringe, fringe, fringe. I am convinced at the end of week one that Edinburgh should be twinned with Gomorrah. It is an evil place without opportunity to rest. I have already hit the wall. In fact the wall is an unholy mess, splattered with the remains of comedians, actors, dancers and street performers. Fringe.

With its castles and its cobblestones, alleyways and steps, monuments and hills and medieval architecture coming out its ears, Edinburgh is a beautiful city. But then so was the capital of Transylvania. And I use the comparison wisely for during the festival, Edinburgh too becomes a sort of vampire town.

Cadaverous comics don't see daylight for three weeks. They surface at nightfall wearing outrageous clothes. They frighten the locals, laugh loudly in a sinister and hollow fashion and agonise about immortality until dawn, surviving all the time on the blood of fellow comics, savaged by the critics.

The fearful religious types who normally live here leave the city at this time. They're not so fearful though when it comes to charging extravagant rents for their hastily vacated rooms.

I know all about the Edinburgh Festival for I've been here many times before. In case I needed a reminder, my promoter left a present for me in the flat I've taken a basket full of vitamins, painkillers, suppositories, surgical gloves, lots of Harpic, Amaonian buzz gum (don't ask), plasters, a pacemaker, a dialysis machine and a coffin (it's an inflatable one).

Things were different back in 1990 when I arrived here for the first time wide eyed and innocent and not very funny with the precocious sketch trio Mr Trellis. For a start, we didn't have a flat. Most performers spend the first few days on the streets of Edinburgh asking strangers to come to their show; we asked them for a place to stay. Eventually some staff at the Assembly Rooms, a major comedy review venue, took pity on us and brought us home. We camped on their floor for 10 days only leaving to shower at the railway station and change our underpants. Giddy, hilarious times indeed.

Now at the Edinburgh Festival, you are not only judged on the quality of your show or on ticket sales. You are not judged on the amount of awards and good reviews and television contracts you receive. You are not even judged on the number of strange people you sleep with. (Edinburgh is knee deep in hormones and sweat; the fire brigade has to row old people to safety.) What matters more than any of the above is the time you finally leave the bar each morning and how few people are still there when you leave. Who did you insult? How many people punched you in the face? And how many policemen did it take to restrain you? This is the true measure of a comic's mettle. This is how you'll be remembered long after your jokes are in a pauper's grave or in some other comic's set.

On these terms, the legendary Malcolm Hardee is the undisputed king of comedy. This week, in what has been a mild avuncular week for him he has displayed an alarming tendency to wander on stage while comedians are battling with a hostile audience wearing a bear costume or more often, nothing at all.

Comedians' necks elongate during the festival by about two inches. This is due to the phenomenon of rubbernecking, otherwise known as schmoozing or Edinburgh Eye. It involves being in the right bar each evening, positioned strategically within view of all the exits; holding incredibly sincere conversations with five or six people at the same time while listening in to five or six others and greeting everybody who walks in or out of the bar. Some veterans of the fringe have heads that are capable of doing 360 degree turns. You can gauge the number of festivals a person has attended by the number of lines on his neck, in the same way as you could tell how rich a Nubian queen was by the number of gold rings on her neck.

You have the same short conversation about a hundred times a day. "How is your show going? Are you getting many in? Any reviews? What time are you on? I'll definitely go and see it next week." It's a far cry from the time I came here six years ago when nobody would talk to me at all not even the other two members of the trio.

It is an intense experience, a marathon, at boiling point, but only second on the comedy cardiograph to the Montreal Festival. Montreal, where I played last year, only lasts a week, compared to Edinburgh's three weeks, but it feels like an eternity in hell where the devil is a hyped up American comic doing jokes about the New York subway. I've never been so scared in all my life. Nobody you meet is less animated than Jim Carrey. Humour is a product like washing powder or guns. Think of an Amway convention or a Republican Party rally, if you want to imagine the fervour and dedication to commerce at the expense of the human soul that is the Montreal Festival.

EACH performer is given exactly seven minutes per night. There are about 20 comics on the bill and hundreds of US TV executives in the audience. One guy went two seconds over his allotted time and was arrested. He was never seen again.

Despite the stress levels (surely about the EU maximums), Edinburgh somehow or other manages to retain credibility. Comics from around the world love to come here. They are part of a festival within a festival, unaware of the 1,300 shows happening elsewhere. Their own shows are running permanently in their heads to full houses and rave reviews.

The highlight of the first week had nothing to do with the festival. It was my trip to Parkhead, home of Celtic Football Club, for their first home game of the season against lowly Raith Rovers. By coincidence, I received a letter the night before informing me that I had been elected as joint honorary president (along with Dermot Morgan) of the Heriot Watt Edinburgh University Celtic Supporters' Club. I was chuffed.

It was a welcome break, a foray into the real world. More like, out of the cauldron into the volcanic pit of bigotry and rage. More than 45,000 demented Glaswegians, each one with an identity crisis more serious than his neighbour, crammed into this magnificent stadium overlooking the city. Hairs danced on my neck when they stopped singing The Fields of Athenry to sing the Irish national anthem like you've never heard it before. Fantastic.

But I can't take any more adrenalin. I've had an adrenalin overdose and there's still two weeks to go. The noise of the crowd at Parkhead was a faint hum compared to the clamour in my skull on the train back to Edinburgh.