Thomas Watson

As a time breach occurred in 1987, the voice of Alexander Graham Bell on the first telephone call saying "Watson come here, I need you," from years earlier was heard bleeding through on the mobile phones of both Sonny Hoskins and Rose Tyler. (TV: Father's Day)

Behind the scenes
Besides being the subject of Bell's first phone call (and thus making him unmistakeably Thomas Watson), no detail is given in Father's Day as to who Watson was or even what his first name is.