For now just going to post a few photos and report what I saw. At lunchtime crowds came down the Strand and into Trafalgar Square then on to Parliament Square.
As this sound system came into Trafalgar Square it was playing Damian Marley's Welcome to Jamrock and Tribe called Quest 's 'Can I kick it?'. People were bouncing up and down. Then I heard it playing Benga and Coki's Night.
Interestingly the BBC's Paul Mason has written today of the 'Dubstep rebellion':
'The man in charge of the sound system was from an eco-farm, he told me, and had been trying to play "politically right on reggae"; however a crowd in which the oldest person was maybe seventeen took over the crucial jack plug, inserted it into aBlackberry, (iPhones are out for this demographic) and pumped out the dubstep.
Young men, mainly black, grabbed each other around the head and formed a surging dance to the digital beat lit, as the light failed, by the distinctly analog light of a bench they had set on fire. Any idea that you are dealing with Lacan-reading hipsters from Spitalfields on this demo is mistaken.
While a good half of the march was undergraduates from the most militant college occupations - UCL, SOAS, Leeds, Sussex - the really stunning phenomenon, politically, was the presence of youth: bainlieue-style youth from Croydon, Peckham, the council estates of Islington' .
(though while there was certainly dubstep being played, as Dan Hancox notes on Twitter, the sounds of grime, rap and bashment were also prominent: 'they banned grime from the clubs, now THERE ARE 300 KIDS RAVING TO POW IN PARLIAMENT SQUARE' (Lethal Bizzle's Pow).
I also heard another sound system entering Trafalgar Square playing John Lennon's Working Class Hero!
There was the usual percussion...... and the not so usual bagpipes:
Later in the evening on the Victoria Embankment there was what seemed to me to be an attempt to use music to pacify the crowd with a National Union of Students bus playing music and then telling people to disperse. Bizarrely they had hired private stewards (SFM) who were blocking the road to stop demonstrators heading down to the House of Commons where a line of riot police were guarding the entrance to Parliament Square near to Westminster Bridge. People pushed past the stewards who got very aggressive - two of them shoved me as I walked through afterwards.
I went round to Trafalgar Square having heard that there was an occupation going on at the National Gallery. Then around half past seven a crowd surged across Trafalgar Square and there was an attempt to set alight to the big Christmas Tree - no doubt inspired by the burning of the tree in Athens during the December 2008 riots.
Although by now police had formed across the road, they didn't seem to know what to do. Oxford Street on a Thursday night before Christmas is full of shoppers and tourists and it wasn't easy to tell who was standing around excitedly watching and taking photos and who was a protester. Every so often the police would surge forward and shoppers, tourists and protesters would scatter, then another stand off started.