Borage
Also known as Starflower, Borage originally comes from the Mediterranean but will grow excellently in the British climate (sidenote: this writer planted some Borage seeds only 10 days ago and has already had to repot them as they exploded out of the soil like triffids).
It’s a sweet herb that can be added to salads and stir fries or used as a garnish in gin-based cocktails (sidenote: yes, this is why I’m growing it).
As well as its culinary uses and its attractive colour, Borage has medicinal properties that add trace minerals to the soil around it, aiding the growth of strawberries, legumes, spinach and tomatoes (some claim it helps tomatoes smell sweeter).
It also detracts certain moths and worms, saving other nearby plants from being eaten, and attracts helpful pollinators like bees.