That looks very like Allium triquetrum ... Three Cornered Leek (sometimes called Wild Garlic but not the true one) Once in your garden it'll spread and spread and you'll never get rid of it ... I'd admire it from a distance ... pick some for cooking with (lovely chopped in salads) if you're sure it's not been sprayed, but don't even consider growing any intentionally
Thanks @Dovefromabove, it's such a pretty little flower......after reading up on it I think I'll leave it there lol. As you said, admire from a distance
Got a patch of it in the garden I’ve been trying to get rid of for years. Definitely one to avoid. Note where you saw it on your walk, it’ll be there next year!
Posts
https://www.wildfooduk.com/edible-wild-plants/three-cornered-leek/
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.