A man wears a hat with two cannabis joints tucked into the strap during a pro-cannabis rally beside the Houses of Parliament in London yesterday.

Guardian News and Media/London

More than 50 people were arrested in connection with a pro-cannabis rally in Hyde Park as the Metropolitan police executed its Total Policing strategy to clear away protesters who had shrouded Speakers’ Corner in sweet-smelling smoke.
The London 4/20 meet-up and protest was due to run until 5pm but by 4.45pm word was sweeping the crowd that “zero tolerance” was about to kick in and officers began entering the crowd to warn people to put out their joints.
“All we are doing is explaining to people that the 4/20 demonstration is over, we want to start returning the park back to normal,” said a liaison officer. “As the evening goes on the tolerance of cannabis is going to be less and less.”
Behind the blue-coated liaison officers, a separate line of police in yellow jackets advanced and pushed the crowd towards Marble Arch. Many smokers quickly finished off the remains of their cannabis for fear they might be picked off by police as they made their way home.
For several hours beforehand, dope smokers had been able to light up with relative freedom - as long as they didn’t stray too close to police.
On the London 4/20 Facebook page, people had earlier said they expected “safety in numbers” would protect them. A steward from Norml - which campaigns for reform of cannabis laws - was overheard telling one group to “keep it discreet and hopefully the police will leave you alone”.
But at least one man was seen being led away from the crowds by police, who were highly visible around the event. Paul Birch, chair of the Cannabis Is Safer Than Alcohol party, told the Guardian he had heard reports that some people were being stopped by police and searched for drugs on the way to the demonstration.
Police said there were 53 arrests, all for drug-related offences. Scotland Yard said 37 people were dealt with at Hyde Park police station, 10 were given a cannabis warning, six were handed a penalty notice, 21 were given police bail and 16 were taken into custody.
Stuart Harper of Norml UK, which planned the 4/20 event, said police were generally accepting of the protest, “but … some people simply allow their exuberance to overtake themselves and police have to act on what they see. Cannabis is unfortunately still illegal.”
The cloud of cannabis smoke from the rally could be smelt half a mile away from the demonstration. A PA brought by the organisers for speeches and music did not work, but many people had brought their own speakers and music.