If you buy only one serum your whole life (and I use the word as the common cosmetics term for thin, viscous skincare treatments, never in the altogether different biological sense), make it a combination of hyaluronic acid and vitamin C. Both ingredients benefit everyone of any age, skin type and skin concern, depending on concentration.

Hyaluronic acid is a no-brainer: it clashes with no other ingredient, aggravates no one (it’s present throughout the body to keep joints, eyeballs and other moving parts well lubricated) and holds water in the skin for a plumper, healthier-looking appearance. I’m just as devoted to vitamin C (generally listed as ascorbic acid), but here, things are more variable. A natural antioxidant, vitamin C helps protect skin against free radical damage, and in most concentrations it quickly imparts a brighter, perkier look. In high concentrations (generally above 20%) it’s shown to have a visible effect on pigmentation spots and melasma, and to help produce collagen. This is certainly borne out by my own experience (see my column in November 2017 on DCL’s C-Scape, £108, or try Garden of Wisdom’s terrific-value Vitamin C Serum 23% + Ferulic Acid, £10, 30ml). However, these high-dose products are often faintly revolting in smell (rotting satsuma in sweaty stocking, anyone?) and texture (grainy and/or sticky), making them unsuited to daytime use. By day, I lower my dose a smidge and chuck in a load of hyaluronic acid.

Balance Me’s new Vitamin C Repair Serum (£32, 30ml) does this, and feels silky and smooth under makeup; it also comes in a pump, to keep the vitamin C, notoriously light- and air-sensitive, stable. I’ve reached for it often. Likewise, REN’s Radiance Perfection Serum (£37, 30ml), which makes me look instantly brighter. A new discovery is Bea Skincare’s Vitamin C 20% & Hyaluronic Acid Serum (£49, 30ml), which feels light, elegant and gentle, despite a whacking great dose of ascorbic acid. Finally, my beloved Drunk Elephant C-Firma, which launches in the UK at Space NK next month (more on this soon), just as Sephora US has stopped shipping internationally. If you’re very oily, skip it and try one of the others. All brilliant, all cruelty-free.