Something in Will's tone makes the Doctor catch himself. "Oh. Right. New body; new rules. Sometimes, even I get in over my head."

He only admits it when there really isn't anything else that can be done. The Dalek, the Forest, the TARDIS... He can fight many things, but nature and physics? There's nothing he can do to fight that.

He takes one long look at the TARDISes and then starts to make his way out. He gives a gesture of his head, a silent invitation that Will can follow if he wants.