Alan Turing

Alan Turing was an English mathematician and during World War II, code-breaker.

Biography
Rachel Jensen and the grandparents of Toshiko Sato worked with Turing. (MA: Who Killed Kennedy, TW: Greeks Bearing Gifts)

Turing designed a Rift Predictor for Torchwood Three in 1941. (TWN: The Twilight Streets)

Turing helped the Eighth Doctor crack an alien code in 1944. (EDA: The Turing Test)

In an alternate timeline Turing was the inventor of the Turing Shroud. (EDA: The Domino Effect)