There is a whole group of women with nothing diagnosably wrong who feel slightly ridiculous complaining. Bloods are normal. Nobody has said the word thinning. The hair is just… flat. Dull. Lifeless. Doing nothing.

It is the biggest group of all and the least served, because there is no condition to search for. The forums have their own name for it — the crap hair club — which tells you something about how seriously women expect to be taken.

Usually it is three ordinary things stacked up. Build-up, from hard water or from product, weighing the hair down and dulling it. Fine hair that has always been fine but now has less to work with. And a cuticle that has roughened over years of heat and friction, so it reflects less light and reads as dull even when it is clean.

The volumising shampoo aisle mostly attacks this by stripping, which gives you a day of lift and a week of dryness. The more useful direction is the opposite one: get the build-up off, get the cuticle lying flat, and let the hair move. Smooth hair has more body than rough hair, which sounds backwards until you have felt it — rough strands snag on each other and sit in a lump, smooth ones separate and swing.

You do not need a diagnosis to be allowed to want your hair to look good. Flat and dull is a real complaint and it has a real, unglamorous answer.