French hair colourist Christophe Robin's Regenerating Mask was one of the first products he ever launched, and remains a best-seller to this day, boasting five star ratings on Look Fantastic and John Lewis (as well as on his own website). This month, the brand introduces the Christophe Robin Regenerating Serum (£44), which contains the same prickly pear oil as the mask, an ingredient that's rich in amino acids to help repair damaged strands and restore shine and elasticity. The multipurpose serum can be used before heat styling (it protects your hair from temperatures up to 230 degrees) to smooth frizz and keep your hair soft, used as a leave-in treatment before air-drying your hair, or applied when your hair is dry along the hairline or over the ends to smooth down fuzzies and make split ends look less noticeable.