Large crowds gathered Saturday in Hyde Park, London, to attend the annual 420 rally.
On April 4, users of the plant in its different forms gather to celebrate its consumption and advocate for the decriminalization of drugs.
In Hyde Park, hundreds of people could bask in the sun while some smoked the substance in public.
While listening to music and enjoying the atmosphere of the festival were clear motivations, many participants wished to advocate for an open discourse on cannabis use.
"It's an opportunity to talk to people who are interested in cannabis," said Barney De Hoedt, editor of a quarterly cannabis culture magazine.
"It gives a chance to connect with people."
He talked about medicinal uses of cannabis and his desire to see its use legalized.
Others have talked about other uses of the cannabis plant, such as hemp, which can then be used to create other items.
Adam Ohman, a hemp producer, explained how this could be used to produce sustainable clothing and household goods.
He talked about "positive uses" of the article.
With respect to cannabis, he called for "decriminalization with some form of regulation".
"I want to see more acceptance," he said with regard to its use, saying that recreational users should not have a hard time for that.
Others spoke of the park's "friendly" atmosphere and seemed mostly determined to enjoy the day in the sun.
Jonathan, who refused to give his last name, said, "I usually come here most years.
"It brings people together, all walks, all ages and all walks of life.
"Most of the time, it's pretty cold."
Another participant, Will Yoxall, told the standard: "It's really good, really nice."
Police had posted signs that cannabis was illegal in the park and was patrolling the area.
The grounds had to be cleared of those involved in 420 to 17 hours.
It was suggested that the figure 420 came from the penal code used by the California police to classify cannabis cases.
Students from a California high school would have organized a meeting at 4:20 pm to find a plot to plant a cannabis plant in 1971.
Weed gatherings and celebrations were held on Saturday throughout the world, up to New Zealand and America.
Cannabis users can go to jail if they get caught.
However, traffickers and resellers are more likely to be sentenced to prison terms.