Redken Blondage Colour Extend Shampoo, €18, salons nationwide

Blonde, highlighted hair is notorious for losing its colour integrity and shine, particularly when it gets overworked and styled, as in the month past. Which is a long way of saying that your Christmas highlights may look brassy and dull by now. Purple shampoos work to counter yellowness, and we found this one to be less drying than most. “I used this twice a week,” said a panellist, “and it gave me a cleaner colour, and will save me having a touch-up until February.”