Police attempts to outlaw the monthly Critical Mass cycle ride through the streets of London unless its route was notified in advance were blocked by the Law Lords today.
The House of Lords allowed a challenge by cyclist Des Kay to a Court of Appeal ruling that the Metropolitan Police had the right to demand prior notice of the ride's date, time and route and the names and addresses of the organisers.
Cyclists who gather on the South Bank and ride through the city to celebrate safe cycling have in the past been handed written notices by the police stating that the event was unlawful because no advance notice was given.
But the Law Lords held that the event, which had no organisers or set route and proceeded on a "follow my leader" basis, was not governed by section 11 of the Public Order Act 1986.
Friends of the Earth Rights and Justice Centre, which acted for Mr Kay, hailed the ruling as "an important victory for the right to peaceful protest and for cyclists to take part in this monthly celebration of cycling".
Mr Kay, described by the Lords as an environmental educator and performing artist, said: "I'm thrilled with this judgment.
"This was a very important case for people like me who have cycled with Critical Mass for many years.
"More importantly, I hope that it will encourage other cyclists to join the monthly rides."
The Critical Mass rides are part of a global phenomenon in which cyclists in more than 400 cities worldwide take to the streets once a month in celebration of safe cycling.
The London ride has taken place on the last Friday of every month since April 1994.
The main legal issue in the appeal was whether the monthly rides were "commonly or customarily held", in which case they were exempt from the notification requirements of the Public Order Act 1986.
The legal action was a result of a leaflet handed out by police at the Critical Mass ride in September 2005, stating: "These cycle protests are not lawful because no organiser has provided police with the necessary notification. Your participation in this event could render you liable to prosecution."
Police lawyers had argued that the rides were not "commonly or customarily held" because, although they started at the same time from the same place on the South Bank, they did not follow the same route.
Therefore, police were entitled to advance notice of the route for the avoidance of public disorder and traffic disruption.
But Lord Phillips ruled today that the ride was a "customary procession", even though it did not follow the same route.
And the evidence showed the Met were usually able to police the ride without difficulty.
Lord Phillips added that an offence under Section 11 of the Act was only committed if the organisers of an event failed to comply with a prior obligation to give details of an intention to hold a "public procession".
Since Critical Mass had no organisers and there was no such obligation, the rides were not unlawful.
The police contended that, if a similar event were to be started elsewhere in the UK, it would be unlawful without prior notice of the route.
Lord Phillips said the Green and White Papers which led to the 1986 Public Order Act were at pains to underline the importance of the right to hold processions and the need for any restrictions to respect that right.
"It is inconceivable that Parliament could have intended, by a sidewind, to outlaw events such as Critical Mass," he said.
Lords Rodger, Carswell and Brown and Baroness Hale also allowed Mr Kay's appeal.