The first of our three 45-minute sets is uneventful, but this is normal. People are still trickling in. Most of them seem to be middle-aged bruisers with long sideburns who won’t leave until they’ve had at least eight pints. Their puddingfed wives are dressed, if not to kill, then at least to inflict grievous bodily harm, in shiny metallic stuff and earrings like Christmas-tree ornaments. Then there are old folks who drink bottles of Stout and stare at us blankly through thick spectacles. God only knows what they're thinking. And at the other end of the scale, sullen greasy-haired youths, a year or two under-age, who'll be either our biggest fans or our worst tormentors.

Most nights, early on, we're ignored, which is good. A bad gig is where they unplug your amps in the middle of a song and throw them out into the car park, and you can forget about getting paid. Hopefully, as the evening rolls on, we’ll get scattered applause, a few shouts of 'bollocks' and 'get off', some drunk howling like a wolf at the back, and a few people dancing. And that'll be a good gig.

But tonight the drinking seems more reckless than usual, and the drunks are not happy drunks. They're oi-what-are-you-lookin'-at drunks, shut-up-when-you're-talkin'-to-me drunks, drunks in imminent danger of getting Out of Order. Even the laughter has an aggressive edge. The barman with the hooks has taken on a sweaty, psychotic look, and the Alsatians are barking. By the time we're halfway through our second set, we're getting nervous. There's something in the air here that we’ve come across before. We can almost smell it. It's hard to define, exactly, but it sure isn’t peace and love.

Right in front of me a quartet of rough girls is getting seriously plastered on vodka and lime and vodka and blackcurrant and vodka and vodka. And one of them thinks it’s very funny to come over now and again, make faces at me, and bang on one of my keyboards, to sow-like squeals of delight from her pals. By the third set, the ladies have been joined by a couple of guys who've drunk enough to make the ladies look good, and something's got to give. The point of no return comes when we hit the Scottish Medley.

And what is the Scottish Medley? Our third set is meant to be rabble-rousing good fun, and on a good night, it is. It includes songs by Elvis and the Beatles that everyone knows, a 50's rock'n'roll medley, and a lot of jokey, clowning stuff, including me slipping behind a curtain and re-emerging (to wild applause and hoots of laughter) as Angus McSporran, wearing a long false ginger beard and a kilt (actually a tartan skirt which used to belong to my mother). We start with 'Donald, Where's Yer Troosers?’' I play a couple of jigs on an accordion, and we end with a rousing chorus of 'Auld Lang Syne'.

This is too much for the Vodka Girls. They have to know what's under the kilt. The one who's been banging my keyboards all night bounces up and starts tugging at it, revealing the rolled-up burgundy flares underneath, and I've had enough. I shove her away; she throws a vodka and orange over me; I throw a pint of bitter over her; and whooosh! the Pen and Parchment Club erupts. A bruiser who wants to defend the honour of the ladies starts a fight with a guy who says they're just a bunch of slags and they were asking for it. Another guy wants to fight him, and another tears off his shirt, revealing rippling muscles, just wanting to fight anyone. Chairs start flying and we escape under the bar hatch and out to the car park just as the dogs are set loose.