Heath Ledger As 'The Joker' : Slightly More Psycho Sir Les?

Was Sir Les Patterson a major source of inspiration for Heath Ledger when he was creating his version of The Joker character for the new Batman film, Dark Knight?

This is the first clip I've seen of Ledger in action that's more than a few seconds long, and it's excellent to finally see something that shows us why so many are so excited about his performance.

To me, in The Joker we can see Ledger playing Sir Les Patterson as a thinner, younger, better dressed man, with less food falling out of his mouth. Obviously, it's not a full imitation of Sir Les, but you can definitely see Barry Humphries' character has been absorbed by Ledger for this role. That's my theory anyway.