I've posted about Rebellion's boss, Jason Kingsley, and his involvement in mediaeval tournaments: Article on Rebellion Publishing's owner
Since then, Rebellion have been posting videos about knights and horses in the mediaeval period, under the channel Modern History TV: Modern History TV
I've only watched a couple of videos so far and found them short and easy viewing. Not particularly intense on details, but enjoyable viewing all the same.
Definitely recommended for research purposes, or just general enjoyment if you're really into horses (I know nothing about them, but think Ghost is a beauty).
Here's a taster, on different types of horses in the mediaeval period: