That's no lizard... that's a bloody dragon! ;-) Only it doesn't breathe fire, it spits venom. You've found yourself a great guard-dragon there! I don't know if you ever saw this, but the best description of Australia's weird wildlife i've heard was was the one by Douglas Adams:

Also he explains about the poisonous saliva from Komodo Dragons, and he's just funny in general :-)

Thanks for sharing the adventures from the Purple Castle my friend! :-)