Harry was the owner of a café in Shoreditch.
He chatted with the Seventh Doctor when he arrived in the café in November 1963. When Ace came into the café, she didn't know how to get his attention, so Mike Smith helped her. Later, Harry left to go to the hospital where his wife was having twins, leaving the café in the care of John. The Doctor's prediction of his wife having twins shows and his familiarity with Harry implies that he had frequented the café in his past time spent around Coal Hill. (TV: Remembrance of the Daleks)
Behind the scenes
According to production subtitles on the 2001 DVD release of Remembrance of the Daleks, Harry was originally planned to have been exterminated by the Daleks.