Prior to having Pageant I 'rescued' a New Forest pony that someone had bought as part of a pair from the sales- it was headed for the slaughter house and so I bought him very cheap.
He was sold as a 4year old and was completely wild out of the forest- so much so that it took nearly a month of hours at a time daily work with him before we even managed to get the sale sticker off his backside!
Anyway, to cut a long story short, the people who bought him didn't have the time to put in to socialising him, and so I bought him to save him going to a dealer who, no doubt would have sold him for meat.
As a relative novice, I didn't have any high ideas about being able to train him to ride, but thought if I could get him handle-able, I may be able to find him a good home.
Five months later, although still a bugger to catch, he was happy to be groomed all over, have his feet picked out, be led out in hand in traffic in a headcollar and had accepted a saddle and bridle.
At this point I made the decision to sell him on to someone more experienced as I was terrified of ruining him! When I sold him it was to a very knowlegable lady who took one look in his mouth and showed me all the evidence I needed that he was at least 7 years old! Several other people had commented that they thought he was older than four, but somehow we had never got round to checking his teeth!! The lady that bought him was however happy to take him anyway and was confident that she could train him easily- she said that I had done the hard work for her by getting him to the stage he was at! Praise indeed for me!
Anyway, I guess the point is that it is possible to train an older horse- even for someone as green as I was then- I hadn't owned a horse myself before and didn't have the faintest idea what I was doing! I read a lot of books that summer!