I was counting back from the fact that the Master just went from the fifth (Derek Jacobi) to the sixth (whatshisname; but it has been pointed out that "Mister Saxon" is an anagram of "Master no. six") -- so poss. actually the 18th and 19th, given the running-out-of-lives whatnot? if this one was the 14th. But whatever. We must not have seen the fourth, then.