Robert McIntosh

 was the Fifth Doctor's assistant for over a year, while the Doctor lived as "Dr Walters" at 107 Baker Street in London during 1866 and 1867. A medical student, he was unaware that the Doctor was anything other than a human academic until after Nyssa returned to the Doctor in late 1867. When he realised that he didn't know the Doctor at all, he was furious with the Time Lord and immediately proposed to end their friendship. (AUDIO: The Haunting of Thomas Brewster)