The serum in question is from The Inkey List. Scarlett is said to use the brand's Hyaluronic Acid Serum in her daily routine, a serum that the brand says helps to make other skincare work harder.

Scarlett's not the only one who praises The Outset Prep Serum, it has also received glowing reviews from online shoppers. One shared: "I have been using this for well over a year now and I couldn ...