The Master nodded. "We could do either of those things. But he made this place - I doubt trapping him here is going to actually upset that much, for that reason, and I'm sure he'll have a back door out we'll have a hard time finding. I always had a way out of Castrovalva," he said to the Doctor.
"Of course you did," the Doctor murmured. "We could repel up to the roof, and side step a lot. Easy."