This year's 'Revolutionary Demo' was advertised for 6 P.M. on Lausitzer Platz in the centre of Kreuzberg. The presence of 7,000 riot cops in the surrounding streets does nothing to suppress the party atmosphere, though a sudden downpour sends everyone heading for the nearest shelter. One Spartakist paper seller ends up looking like a drowned rat and all his papers are left in a soggy mush . . . if there is a God, he seems to have it in for the Trots!

The action kicks off when a couple of masked figures appear on the roof of a neighbouring building with flares held aloft. Then, on the stroke of 7:30 P.M., the Black Bloc surges south with a huge phalanx of Robocops in tow. Anarchists have been playing cat-and-mouse with the police for twenty-five years in these streets and the authorities have taken every possible precaution to seal off any escape route. The demo is fairly big - the local news says 10,000 - but we are trappped in a moving kettle with lines of cop vans and water-cannon sitting across all the major thoroughfares.

Suddenly, there is an almighty bang. It sounds like a window going in but it turns out to be an extra-loud firecracker. We move briskly through the streets for the best part of an hour and we end up on Lindenstrasse, just north of the Jewish Museum. The lead cop vans and the press photographers have already turned onto Markgraffenstrasse but the Black Bloc has other ideas. Scuffles break out with the police escort and seven red-faced activists are dragged from the crowd. The area to the immediate south is filled with loose cobblestones and rubble. It is too dark to see the missiles flying but the snatch-squads have their work cut out and it is clear that the cops are coming under a steady hail of projectiles. Now the chant goes up: Ganz Berlin Hass die Polizei! - All of Berlin Hates the Police!

The riot cops surge back and forth for a few hectic minutes and I briefly get trapped in a little pocket of masked protestors that the police have pushed up against the front wall of the museum. Extricating myself from this tight spot, I head over to some bushes where a circle of cops are standing in a defensive formation. A prone anarchist is lying on his back with his arms out by his sides. He is wearing the 'uniform' of the Black Bloc - black combats, black hoodie, wraparound sunglasses and he is clearly unconscious. The cops try to stop onlookers from getting too close while the paramedics do their thing. A thumbs-up sign indicates that the patient has a pulse so we aren't looking at another Carlo Guiliani . . . the absurdity of the situation is underlined when a drunken passer-by whips out his tackle and relieves himself in the bushes, just a few inches away from the police line.

In the background, the snatch squads are still raiding the crowd for miscreants. The tarmac is littered with cobblestones and broken glass but the cops are pulling out now and the Black Bloc has disintegrated. We trickle back towards Kreuzberg in little groups; there are a few beery chants whenever a line of police vans hoves into view, but otherwise all the energy seems to have ebbed out of the crowd. Kreuzberg is heaving with party-goers but there are masses of cops blocking the entrance to Kottbusser Tor U-Bahn station and we have to trudge three blocks eastwards to find a station that is open. There is still the possibility of further action in Kreuzberg but my knees are hurting like hell from all the walking and I decide to call it a night.

I have a nervous moment on the S-Bahn platform when a burly man starts staring in my direction and mouthing something into a concealed microphone. Oh bollocks, he looks like an undercover cop. I consider legging it but I'm too knackered to run so I let him follow me into the carriage. However, he gets out after one stop and I realise that he was just a gay guy cruising me on his way home from work. Just another day in cosmopolitan Berlin.