Robert Stephenson

Stephenson was a renowned 19th century British engineer. When the Eighth Doctor brough Madeline de Roche into his TARDIS, she asked if it was a new design by Stephenson or Brunel. (AUDIO: Other Lives)

Behind the scenes
This individual is most likely. His father, George Stephenson, an acquaintance of the Sixth Doctor, was also a renowned British engineer, but the elder Stephenson was dead by 1851, when Other Lives takes place. Only a surname is mentioned and the story does not draw a connection between the two men.

He was previously referenced, again as just "Stephenson", in the board game The Universe Marathon, where one of the squares sees the Doctor hitching a ride on Stephenson's Rocket to get to his destination slightly faster.