More chance of shitting in the queens handbag 

There is a very slim possibility the task you would like to perform, will be completed satisfactory.

"Breeding Mongolian Traffic wardens with a hybrid Bagder to create a kung fu red blooded super race?!" -

"You got more chance of shitting in the queens handbag!"

More chance of shitting in the queens handbag by Professional Biscuit Thief December 10, 2009