The Monk's logbook

The First Monk kept a logbook, a "sort of diary". It was recovered by Steven Taylor and Vicki Pallister in his own TARDIS.

They managed to read that he had met Leonardo da Vinci and discussed with him the principles of powered flight; he had put two hundred pounds in a London bank in 1968, and he had nipped forward two hundred years and collected a fortune in compound interest. (TV: "Checkmate")