Sir John Sudbury was a British politician. From the early 1970s (PROSE: The Eye of the Giant, The Scales of Injustice) to as late as 1989, he ran C19. (PROSE: Business Unusual) In the 1970s, he was a junior Defence Minister and MP for Woodhaven. (PROSE: The Scales of Injustice)
Sir John was the financial liaison between UNIT and the British government. (PROSE: The Eye of the Giant) He played bridge at the Pemburton club with the Third Doctor and Lord Rowlands. Circa the 1970s, he came to UNIT HQ to discuss their funding. He was informed of the rogue C19 Vault run by his secretarial aide, and whatever had remained up there was subsequently gone. (PROSE: The Scales of Injustice)
Circa 1982, Sudbury asked the Fifth Doctor to investigate the disappearance of a Concorde aircraft. (TV: Time-Flight) In October 1983 Sudbury attended the UNIT reunion with Lethbridge-Stewart and made a speech about his achievements. Years later, he brought in the Doctor to investigate SenéNet. (PROSE: Business Unusual)
After this incident, Sudbury officially died of a heart attack but, given that his health was excellent and his death sudden, he was probably murdered. (PROSE: Instruments of Darkness)