Professor (Dr. Who's Time Tales)

A Professor observed two other scientists' experiments with time travel. Witnessing their success with propelling an iron ball back in time, he admitted that their theories were sound, something he had previously denied, but implored them not to continue their experiments, for fear that even a small object might alter a significant historical event and alter the whole of Earth's timeline. They derided him as an "old fool" and he stormed off. The Fourth Doctor later became aware of this "time tale", bemoaning, in his telling, that no one had listened to the Professor until it was too late. (COMIC: Dr. Who's Time Tales)