Walking along Tottenham Court Road on a recent, rare, trip to London I was struck by a sweet, pungent odour, which I couldn’t immediately identify. The answer arrived moments later while cutting through a dark Dickensian alley en route to Oxford Street. My way was blocked by a group of wild-eyed, ragged looking men, all smoking marijuana. It was like a scene from Michael Jackson’s Thriller video, except genuinely scary. The men were staring at me as if I were a trespasser.