Euphorbia Mellifera or Honey Spurge...there is an enormous one growing in the Gardens of Heligan, in a little courtyard garden. When it's in flower it has the most fantastic honey smell and bees absolutely adore it. I have one on the corner of my garden, after searching for it for ages, and it can be a bit of a thug! All I'd ever read about it was that it was a little tender....NOT in my garden in Plymouth...it has to be chopped back regularly! Roots easily from pieces pulled from the base, or layered. Seems like it needs a corner where it can do its own thing, to flower at its best. Be careful though, like all spurges/euphorbia, it has a milky sap than can cause irritation. Wouldn't be without my lovable thug though!