(written from a Production point of view)
He began his acting career in the 1950s and featured in a number of war movies through the 1960s and 1970s, including the WWII TV miniseries The Rhinemann Exchange (1977, with Stephen Collins, Rene Auberjonois, John Hoyt, and Katherine Woodville).
Kemp appears also in the famous World War II sagas Winds of War and War and Remembrance as Brigadier General Armin von Roon. Several other Star Trek actors appeared in the series as well, including William Schallert, Natalia Nogulich, Logan Ramsey, Paul Lambert, Charles Napier, Bruce French, George Murdock, John Rhys-Davies, and Steven Berkoff.
In 1975, he guest starred in the sci-fi series Space: 1999, starring Martin Landau, Nick Tate, and Clifton Jones, in the episode "Voyager's Return", which is similar in theme to the Star Trek: Voyager episode "Friendship One". In a 1984 episode of Granada Television's The Adventures of Sherlock Holmes, "The Adventure of the Speckled Band," he played the main antagonist, Dr. Grimesby Roylott, the tyrannical stepfather of the character played by Rosalyn Landor.
His most recent role was in the Conan: The Adventurer television series and movies in 1998.