Where was the Master wanting to be taken? Some place shared by him and the Doctor, no doubt. He watched the Master's footing carefully, waiting for an opening. But the way that he was brandishing his weapon made it seem as if he was poised to strike him for trying to retaliate. Still, he had to try. Any attack from the Master would certainly be better than the TARDIS crashing.

Jack pulled himself up just a bit and twisted his hips to sweep the Master from the back of the knees. Maybe if he fell over, he'd drop the knife, too!