My horse continually rears in the lorry?

I have a very bad tempered and argumentative thoroughbred, we were leaving for a show, he could see his two mates in the field and just went bananas striking out- which he often does when he's angry, does it in the stable when he's left alone. He then reared up and got stuck up on the tack lockers- now i don't know whether he meant to get up there or if he just struck out high and then found himself up there. He was dancing on the ceiling and kicking the wall. I had to get in there and try and bend his legs to get him down, it was all quite terrifying!! He was up there for quite some time too. Does anyone have any suggestions on this as I can't keep playing that game again! He did it at a show once. Someone at the show said if its anger hobble him but if its panic don't as he'll kill himself!? Not mad keen on hobbles to be honest. Ideas/comments please!