He knows that Saxon was a madman but a genius, he could have done anything to the Gate, and he did
I know but Joshua Naismith said land mines. How would the Master've have land mines if he's homeless?
It was just an example, he had no idea what the Master had done.
I know it was an example but what ever gave Naismith the impression the Master could've created and set land mines or had any on him considering he was homeless?