Horatio Chinn

Horatio Chinn was a Ministry of Defence official and head of an inquiry into UNIT.

Biography
Horatio Chin (PROSE: Doctor Who and the Claws of Axos) was given full security clearance by the Ministry of Security, but the Brigadier wouldn't tell him about the Doctor's origin and American UNIT agent Bill Filer shunned him as a security risk. Chinn was completely unaware who was, no matter how many times he insisted. (TV: The Claws of Axos)

What he didn't know was that the the minister loathed him and only gave him the UNIT task to get him out of the way. As the Ministry was clashing with UNIT at the time, it was hoped that either Chinn or UNIT would be destroyed by the other or, at the least, cancel each other out. (PROSE: Who Killed Kennedy) The Defence Minister would go as far as to imply to Chinn he was "our man on the spot, in more ways than one". (TV: The Claws of Axos)

Chinn was investigating UNIT when Axos came to Earth. (Before contact was made, he inserted himself into UNIT's tracking operation and tried to command it; all his orders were things UNIT were already doing or made the situation worse) He was very impressed by the Axonite, and saw all the possibilities for Great Britain if they got a monopoly of it. When the Brigadier tried to take control of the Axonite samples, Chinn called in the regular British Army to take over and arrest UNIT under the Emergency Powers Act — a move that was illegal. He went on to prevent a search for Bill Filer in case it interfered with the Axonite deal.

The UN made sure that he did not get his wish for Axonite as a solely British product (much to the annoyance of the Ministry, as Chinn hadn't stopped news leaking out). He was forced to organise its worldwide distribution. The Defence Minister let Chinn know that if he couldn't sort it out, the ministry already had his resignation letter pre-written and waiting Chinn's signature.

When Axonite proved to be dangerous, Chinn was found by the Brigadier slacking off and claiming he'd been trying to "do something" to stop Britain (meaning himself) being blamed. He would be trapped in the nuclear power plant during the Axos attack but managed to escape with the remaining UNIT survivors when it exploded. (TV: The Claws of Axos)

Accounts say Chinn either took the credit for stopping Axos (PROSE: Doctor Who and the Claws of Axos) or got all the blame in an official report, forcing him to take early retirement. (PROSE: Who Killed Kennedy)

The Brigadier later tried to contact Chinn for help when government budget cuts threatened to shut down UNIT's UK branch. Chinn's assistant answered the call but Chinn refused to speak with the Brigadier. (PROSE: Where the Heart Is)

Personality
Chin was a nationalist, loathed by the Doctor for having "England for the English" (the Doctor's words) views; Chinn complained that the United Nations were "high handed" ever since UNIT started. (TV: The Claws of Axos) While he saw himself as a bureaucracy-busting troubleshooter, he was seen by the rest of the government as a buffoon and his only real skill was stroking the egos of insecure ministers and parliamentary private secretaries. As a result, he would bounce from department to department. (PROSE: Who Killed Kennedy) His reports were known for being garbled. (TV: The Claws of Axos)

Behind the scenes

 * It's not stated outright in the episode but Chinn is usually implied to be a civil servant. This is officially stated in both the novelisation (and Who Killed Kennedy following it), but in these he's part of the fictional "Ministry of Security" that wants to bring all the intelligence agencies together. Since UNIT's UN status complicates this, the Minister of Security has sent Chinn in to cause problems.
 * Chinn's first name was not given on-screen; it is used only in Terrance Dicks's novelisation of the story, as well as in Who Killed Kennedy and Where the Heart Is.