BBC Radio 4 Law in Action: Protesters or law-breakers?
When is a demonstration not a demonstration? That effectively is the intriguing question that the most senior judges in the country will have to decide next week, writes the BBC's Clive Coleman.
The case centres on the Critical Mass Cycle ride, a mass bike ride around the streets of London held on the last Friday of each month. The ruling could prove highly significant to many others wanting to hold marches and processions.
To find out more about Critical Mass, I dusted off my bicycle clips, got on to my 20-year-old boneshaker and wobbled across Waterloo Bridge to the assembly point on London's South Bank. It proved to be a somewhat surreal experience.
FIND OUT MORE...
Law in Action's look at the Critical Mass bike ride is on BBC Radio 4, Tuesday 14 October at 1600 BST
In the balmy autumn sun light, I chatted with a cyclist dressed as a crocodile, saw people arriving horizontally on a collection of ornately decorated "recumbent" bikes, and gasped in awe as cyclists literally passed over head on raised, "stilted" bikes.
The law on public processions is governed by section 11 of the Public Order Act 1986. It requires organisers to notify the police in writing of their intention to hold a public procession, and to provide details of the date, route and their own names and addresses.
The hundreds of cyclists who take part in Critical Mass say that, although the event is a regular occurrence, no one organises it and the route is never the same. And crucially it claims that it comes within an exception to the notice provisions because its event is "commonly or customarily held".
That exemption exists because the details of something that is commonly held will already be known to the police, and so notice is not required.
It's now up to the the country's most senior judges, the Law Lords, to decide if a public procession that is apparently not organised and follows a random route, is one that can be defined as "commonly or customarily held".
Back on the South Bank a rising cacophony of claxons, horns and whistles sent us on our way onto the roundabout at the end of Waterloo Bridge. Traffic from five different directions was instantaneously halted as hundreds of us made our way across the bridge. It seemed a little surprising to see that there were no police in evidence, though the motorists took it all in a rather good humoured British way.
Global event: Critical Mass cyclists in Budapest
Critical Mass claims to host these sort of rides in 400 cities around the world, and they had been happening without incident in London for 11 years. But in 2005 the police started handing out warnings which informed those taking part that they required advanced notice detailing date, time, route and the names and addresses of organisers.
"It was very strange really," says cyclist Des Kay. "We got letters from Met police saying what we were doing was illegal, after 11 years of riding round quite happily. And we felt it needed to be challenged."
It was. After conflicting judgements in the High Court and Court of Appeal, it is in Des Kay's name that Friends of the Earth, an environmental pressure group, is taking the appeal to the House of Lords.
The police take issue with Mr Kay.
Inspector Nick Rowe of the City of Westminster has been responsible for policing the rides. He says the police believe those involved in the mass cycle are going out "with common cause to demonstrate and as such they should give us notice of where they're going to go."
And he thinks Critical Mass is at least part organised.
"There are many different ways in which an event can be seen as being organised and there are certainly people there who have a pretty good idea at the start of the evening which way they're going to go."
Taking to the streets in London in 2005
And while the Critical Mass rides have no overt political motive, there seems to be an underlying agenda, he says.
"It's very interesting that when something is in the world media agenda - such as the war in Iraq - [they] turn up there and shout things at the US embassy," he says.
But for those who don't feel inclined to mount a push bike on a Friday evening, is there a broader significance to this case?
Professor Helen Fenwick from Durham University says tat the decision of the House of Lords could have consequences for other public processions.
"Assuming police are successful it puts organisers in a difficult position," says Ms Fenwick. "Section 11 is difficult to comply with in general because when you are trying to organise a march, it is hard to be sure if the march will stick to the route or not, how many numbers will turn up, exactly what will occur. If the police are successful it could have some deterrent effect on organisers of demonstrations."
Food for thought, even if all you want to do is cycle around London dressed as a crocodile.
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