I have been trying to work out the title of a Doctor Who book I read about 25-30 years ago.
The premise of the story is that the Doctor (not 100% on the incarnation but think 3rd, or 4th) takes his companions to a planet that is considered the most peaceful, idyllic vacation resort in the universe.
On arriving the inhabitants display random acts of aggression to each other, the Doctor and his companions. On investigating he discovers finally that an alien is manipulating the inhabitants for his own aims with a weapon, I believe he is on a ship that is in orbit over the planet.
I am assuming this was published as a book and released as an episode on the TV I would have read the book around the time of Sylvestor McCoy (that's when I got into Doctor Who and used to devour all the books of the old episodes as they where released). I want to say it was Baker or Pertwee as most of the books available to buy at the time were from this era.