Why do some celebrity perfumes – think Ariana Grande, Britney Spears – stay popular?

There is a particular kind of deja vu that comes from a stranger’s perfume, when a scent – sugary-sweet in a lift, soft and creamy on a person’s jumper, flowery from a hug – drifts past and you know it long before you can name it. Chances are, a few of them come with a celebrity’s name. Famous names have long sold perfumes, intentionally or not. When Marilyn Monroe said in 1952 that Chanel No 5 was all she wore to bed, she did more for that bottle than any advertisement could, despite never...