I know for combined driving Prince Phillip really started it in England (I want to say back in the 50's-60's). I have some older books from the 60's and boy has it ever changed!! They used to use pleasure type vehicles and the judge would drive with them in the front seat. They always looked so terrified! Now the hazard judges stay in the hazard and judge/time each competitor as they enter and exit each hazard (there are usually 6-8 hazards at each show so you need a lot of hazard judges. Perhaps thats why they used to go with each competitor at first. You need about 3 judges for each hazard so it really adds up). He made up the sport, pretty much like eventing where you have the dressage the first day (converting the scores you get to make them as low as possible), the marathon the second day and instead of stadium jumping for the third day, it is a cones course.
I'm not too sure about pleasure driving. I'm sure it goes back to England though...
I have many books on combined driving and it is a very interesting sport! I love it!!