Hi all. I'm hoping someone can give me some advice on how to control a jittery 4 year old mare when out hacking. I'm a novice rider, having been round horses when I was around 12 and only returning to it around 6 months ago. The mare in question belongs to my friend and we have had a tough time with her rearing both in and out of saddle, even getting a behaviourist out as she would rear whilst being led then bolt off. We eventually bought a Monty Roberts head collar and it has worked brilliantly - we can even walk her past stallions and other mares that are running up to their fences as we go past. But, when we hack out she is very very alert, head high and always looking around her. If we come across another horse she will start playing up, walking backwards, threatening to rear, and if I try walking her on she feels like she's going to take off with me. This is despite being out with an older, calmer mare and more experienced rider. How can I get her past this and control her when it happens?