Diamonds are a girl's best friend on Valentine's Day, especially when they're lab grown stones that are ethically sourced, like one used in the Leo & Lumi Isobel Necklace (£250). As a gift, this delicate piece is a sure win as it goes with anything, compliments a majority of outfits (well, minus roll necks, maybe), and looks beautiful on its own or layered with your favourite chains.