I'd get him off the rich grass. I'm wondering if he's beginning to founder and has sore feet. That would account for this behaviour. He was a good boy while in his transition stage but now he's testing you to see what he can get away with. I'd do lots of groundwork turning lots of turnbacks while lunging but 15 min is plenty. Do everything you can think up to get him moving away from you, his hinquarters, his shoulders, forward, back. By pushing him around like this you are the dominant one. I'd do this every day for a min of three days, preferably 5 to really drill it into his head. No riding during this time.
He's now been off that paddock since that day, he's now back on my property but up the road on different grass, now I have to find a way to stop einstein over there jumping my reels!
He stays in his paddock just not his allocated part.
He's back to his normal behaviour in the paddock, and I've been lunging him everyday instead of riding him since he got back and unfortunately I discovered a loose shoe yesterday, so now I'm going to have to go through the struggle of finding a farrier, my one has just had knee surgery and all the others are booked out, might have to ask my neighbour, he's done my horses before. -I would pull it off myself, grandad gave me the tools to do it, but i'm not a qualified farrier and i'm a bit iffy about pulling it off myself.
-The lunging we've had to work on a lot as when I first lunged him he thought lunge meant oval, and on one side of your oval your supposed to run over the rope holder, then pull them across the paddock on your other side. He's since discovered this is not the case, and lunge means circle
He's gone back to his normal cuddly self in the paddock, but I try not to let him be too cuddly because I don't want to baby him incase he thinks he can cuddle his way out of it, and he probably would try it to
I'll start doing what you've said once I've done something about his hooves :)