Now we all know this plant, maybe mistakable with other umbelifers when young but certainly not when it grows up!
you can sometimes come across forests of the stuff
The purple blotches reminescent of other dangerous umbels
it's the sap that is the most immediate danger with this plant,blistering your skin when exposed to sunlight, I did experience a little of this when cutting into this one, a little sap landed on my hand and after a few minutes the skin raised and blistered slightly just like a nettle sting, but I really wouldn't want a lot of skin exposed to this sap.
When dry the stems make good little possibles containers! some of them being as large in diameter as your arm!