Lutra has the right idea - if you see a small plant that you even think might be a young Giant Hogweed, stamp upon it.
If you are unhappy about identification, then a study of the Umbelliferae is a must, but be warned, it is not easy
There are plenty of good foods in the family. Chervil, wild carrot, pignut, fennel, wild parsnip, samphire, alexanders,, sweet cicely, wild parsley etc
Equally there are some really poisonous nasties Cowbane, Hemlock. Hemlock Water Dropwort, Fool's Parsley Giant Hogweed etc
Neither list is meant to be exhaustive, and there are plenty in between ranging from bland but harmless to vaguely unpleasant.
Messing with Umbells is a bit like messing with fungi - fine if you know exactly what you are doing, dangerous otherwise.
Oh, and if anyone thinks they know the difference between Hogweed and Giant Hogweed,, bear in mind the two species hybridise and the hybrids show intermediate features. These hybrids are common and getting more widespread.
Edited by Vagabond, 13 April 2017 - 04:43 PM.