This afternoon I got home around 4pm. I went out to the yards, gritted my teeth, and led the ponies out to the paddock and let them go. I was really nervous they would play silly buggers and the colt would follow, but maybe not know about the fences. Actually it was much less drama than I was fearing.
Here's a video of the first few minutes - Honey is being a bit of a bully and they were kinda pushing him into the fences a little.
Hokey Pokey then started following him around and nibbling his flanks and then biting his neck quite hard (I think he wants to play?), and the colt just keeps doing the "I'm a harmless foal" chewing action and walking away. I feel really sorry for him but I think he's coping okay. I'm sure they'll settle down soon. I suspect the two boys may end up being mates.