Theophilus Tolliver

Theophilus Tolliver (who preferred to be called Theo) was a British inventor in the 19th century who invented a time machine. During his second trip through time, he was captured by Andron, taken to 3550 New Britain and imprisoned. After the Third Doctor was imprisoned with him, they worked together to escape execution and overthrow Mar-Kom. Afterwards, Theo returned to his own time, where he told his friend H. G. Wells about his adventures. (COMIC: The Eternal Present)

Behind the scenes
The implication is that Theo is the protagonist of The Time Machine.