What is a cabbage tree?

I'm resurrecting this old post to clarify just what a 'cabbage tree' as we know them, actually is.

In the southwest of England they are known as Torquay palms, but in fact are not a palm tree at all. They are a giant lilly.

They like wet conditions and so I planted out a whole lot in a boggy patch on our property. These ones are about 6 years old:

Small boy in photo shows scale!