Little is known about Mike Yates' background before joining UNIT, although he probably attended a private school. Our earliest information about him tells us that he was seconded to UNIT straight after the Black Thursday Operation, and that he was involved in the clear-up operation after that incident. After several months in UNIT doing mostly clear-up operations, Yates was promoted to Captain. This was shortly after the Cheviot Hills Shutdown, which coincided with an increase in UNIT's budget.
Yates served as second in command of UNIT UK until his involvement in the Operation Golden Age Scandal, after which he was given the option of retiring quietly from UNIT, which he took. Yates was later involved in The Mummerset Monastery Affair and was also recalled as an undercover UNIT agent during the Black Star Era.
Interestingly, sources from among former Black Star activists suggest that Yates was very attracted to their cause of anarchy, which raises severe questions as to how UNIT picked their senior officers. A force dedicated to react, assess and respond to outside threats cannot possibly allow a senior officer with that sort of sympathies and still hope to do its job effectively, no matter what the threats referred to in its mission statement are. To have a senior officer actively sympathising with anarchist and subversive groups is to invite disaster on any military unit, let alone one which fulfils a role such as UNIT's. For an elite group to have such lax screening policies is total stupidity, so why was Yates appointed?