Actually not a cactus - it's a species of Euphorbia, many of which are cactus look-alikes (a nice example of convergent evolution in similar climates).
Thanks for your reply can you tell me its exact name as I would love it to be a tree for insurance purposes. once again thanks for your help. WBl
Whether it is a tree or not is not much related to its identity; a tree is a growth form, not a botanical classification. The usual definition of a tree is "a woody perennial plant which can attain a stature of 6m or more on a single stem" (A F Mitchell 1974, Field Guide to the Trees of Britain and Northern Europe); I'd think your plant will be capable of that when fully mature (I'd guess it is about 4-5m tall now?). Someone with more experience of the genus Euphorbia than I have is sure to be along soon and identify it to species.
You are not being very helpful. Exactly where was the picture taken? It most certaily wan't anywhere in England. It may be listed as a tree in some regional flora if we knew where the plant is.
