Katie points to the policeman cycling among sunbathers in the park where she used to go “blazing”.

“Let’s see who he stops,” she says, following the officer in the fluorescent vest as he heads towards an ordinary young man, sitting on a bench. “There - straight for the smackhead.”

The 21-year-old former cannabis user started coming to Kidswell park in Maidenhead to smoke when she was about 12. Cannabis use has become so normal in the quiet Berkshire town, that smoking a spliff in public is almost acceptable.

Her friend, Calum, is a case in point: “I skinned up in McDonald’s the other day, and no one said a word.”

They think that reclassification will make little difference to Britain’s collective habit. Calum, 16, said: “I was told it was class D, and to be honest I’ve never really known whether it was B or C, or when it was changed. Half the kids these days don’t know either. And they’re not going to care.”

Police enforcement would create the biggest deterrent, Katie said. “They should arrest people and stick them in the cells to think about it.”

Calum disagreed. “If I got done for cannabis, I would laugh in the judge’s face. Putting me in prison just for smoking a joint? That’s just stupid.”

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