Mark was born in October 1964 in the British Military Hospital in Hannover, Germany. His late father, Peter, was serving in the British Army at the time. His late mother, Ulrike, hailed from the part of Germany which is now in Poland.
Mark grew up with his brother, Dominic, and his sister, Antonia, and was educated in the state sector at Reading School. He later took a degree in law at St Edmund Hall, Oxford in 1987.