Now is another season of our heated discontent

BRITISH RIOTS, like the first cuckoo, the Glastonbury Festival, or fireworks night are a seasonal affair. A sound of breaking glass and the cracking of heads are a peculiarly British way of saying the summer has arrived.

"The weekend's riots are part of a much larger and often honourable tradition of such seasonal outbursts of political dissent," said the historian Brian Brivati. "They can be traced back to the 18th century when the price of corn after the harvest triggered rioting. It came from a heady mixture of cider and warm weather."

Eighteen years ago, Brixton and Southall in London and Toxteth in Liverpool burned. In 1985, it was the Broadwater Farm estate in Tottenham, north London, which cost the life of Constable Keith Blakelock. In 1991, the deprived youth of Blackbird Leys in Oxford, Ely in Cardiff and Meadow Well on Tyneside deprived their communities further by setting fire to local shops and property.

But Friday's shenanigans came out of a slightly different tradition. This was not the spontaneous violence of a community in reaction to a perceived affront by the state. This was a violent fringe that has repeatedly exploited protests intended to be peaceful.

Within the world of eco-warriors, anti-racists and extreme left-wing politics there is a hard core of protesters who enjoy a good punch-up with the police. The City has been targeted before. Anarchists' groups such as Class War organised the Stop the City events of the late Eighties. In 1990, the poll-tax protest turned into a wide-scale riot and sealed the political fate of Margaret Thatcher.

So what did Friday's violence mean? "It is hard to see their aims," Mr Brivati said. "This is not like the poll-tax riot where the issue was clear and reflected a broad swath of agreement from little old ladies in the counties to New Age travellers."

Certainly, it is hard to believe they were motivated purely by international debt. "Were the rioters seriously saying: `You must dismantle the whole edifice of Western capitalism by 4 o'clock or we are getting on our bikes?" asked Mr Brivati. "I doubt it. One can speculate that there is a groundswell of disappointment with the Labour Government. But without an issue like the poll tax, it doesn't represent any real challenge to Tony Blair."

History shows that riots usually only cause long-term political problems when the state over-reacts, according to Mr Brivati. "Mostly, these things blow themselves out very quickly," he said. "If you look at the riots of the 18th and 19th century, the state usually let the protesters have their outburst. It was only when they cracked down, like the Peterloo massacre [by cavalry in Manchester in 1819], that serious political problems followed."

t In an emergency Commons statement yesterday, Jack Straw, the Home Secretary, condemned the disturbances as a "wholly deplorable outbreak of violence" which had been "plainly premeditated" by the organisers of the demonstration.