Horse bolts on a loose rein - advice please :(

[Cuddly Connemara]

I have a Connemara horse , he is 15.1 and 9 yrs . After I have worked him hard I give him a loose rein and he suddenly spooks on the loose rein and takes off - it's really awful because I have no contact at the time! He's been checked by the physio and by the saddler. I'm not going to lie when I got him he wasn't broken properly ( I wasn't aware of this at the time) and some attempt had been made previously by somebody to break him , as he still to this day hates being mounted and won't go near a mounting block - he also is scared of tall men and high jumps. I've had him for two years and he's come so far but, just in the recent month or so he has started bolting like this - anyone experienced anything similar to this . Any advice much appreciated

 

[be positive]

He sounds as if he is very insecure, having had a bad start in life often stays with them in some way however hard you try, I would stop letting him have a loose rein for a while if that is the only time he tends to spook and shoot off, sometimes they are just taking the mickey but with him it sounds more like a panic reaction, he spooks then runs because he is worried about the consequences, maybe in the past he got hit for spooking and he remembers it.
I would only let him have a long rein , not loose, in walk at the end of a schooling session when he is totally relaxed and a bit tired, allow him to stretch on your terms but keep him on a contact and asking him to work in some way all the time, flexing either side, doing some small circles and turns so he is stretching nicely but not able to do his own thing, you need to get his confidence so that gradually he relaxes and learns that he has to still listen, if he does spook try and stay calm and give him a pat, use your voice to reassure him that spooking is not the end of the world and that he will not be told off for doing it or for running away if he does go, if you always have some contact it should be easier to stop him without either of you overreacting or getting upset.

Regarding the mounting I would be looking at trying to sort that out, can you get back on after you have ridden a while? if you can then that is the time to work on helping him get over this issue, if you have not tried then see if you can and spend some time after riding getting on and off, praising him if he stands well, the tall men and high jumps may be more tricky and possibly less of an issue as long as he copes with farriers and vets.