Saddle and stepped up on Jupiter today.
While he may have had someone sit on his back, I guessed by his lack of reaction to leg cues, even in so much as to walk forward, I did not think he had been ridden before. His owner has since informed me that I was correct, he had been saddled in the past but never ridden.
He was perfectly calm and quiet and by the end of the 20 minute ride he was moving forward, left and right from leg pressure, though stopping/backing were a little iffy, as I only had a side pull on him.
I will put a soft snaffle in his mouth next and if he takes to it as easily as he did being ridden, we should be able to move his training forward quickly.
He still has a fair little amount a weight to slip and muscle to build before we can really push him at all, so we will have plenty of time to get him used to both saddle and bit. By then his balance will be where it needs to be to and away we go.
I can hardly wait.