If you are sure he is having negative associations with the halter, first try a different halter - sometimes it is that simple. However, if that doesn't work start all over again with him as if he is untouched. Use a rope to rub over his face, particularly around the areas that a halter 'sits' - when he is calm and quiet move away (see Montys Advance/retreat explanations). You can then progress to "wrapping" (NOT tying) the rope at various points so that he feels a little pressure (mimmicking the halter); then progress to a rope halter (only because it has no noisy clanky bits). When you can get al halter back on and off again I suggest going to a Dually halter and then you can start working on him. I find it so hard to explain these processes in words, so much easier to show! Please tell me if I'm not making any sense :-) Above all, be patient, it will come if you are kind and consistent.

Thank you for your reply I will start again with him and secure our bond, then start with the rope.

I suggest rewatching the videos on letting your horse catch you, only advance when he is looking away and then lower your eyes and half turn away when he looks at you. Pretend like you don't care to catch him. When you get close enough touch or stroke a little then turn and take a few steps away. Remember your telling him to walk away if you look square in his eyes while your walking up to him.

I had my horse loose in the arena while we were cleaning her pen and I started practicing doing the little arcs like Monty showed on the video, not even paying attention to where the horses were and they both walked up to me like I was asking them to, I gave both of them a little rub on the forehead and walked away.

Ooops, I should have added, start doing the little arcs and have the halter in your hand a few times without catching your pony. Just kinda hang out with the pony looking down, or just rubbing with your hand or touch his neck with the halter then walk away.

Just spending time with him after such a traumatic event will help. Just walking by him with eyes down and sitting quietly in his yard. When he comes up just quietly stroke him with eyes downcast. Maybe start feeding him smaller amounts more often so he is used to you around him and knows that you look after him. As Vicci suggest - if it is the dually that he is scared of then try the rope halter then you can always pop the dually over the rope halter if you need to but if he is only a pony and only 15 months old you probably don't need the dually at this point of time. Just use the rope halter to lead him around etc. Recently my little shetland, Chester, who is icredibly quiet had a piece of chaff caught in his eye which then became infected and it was very painful. When I couldn't get it out myself I took him off to the vet. He was very good but it was very scary for him as we had to go at night and he was in a lot of pain. Next day he was scared of me and wouldn't come near me so even a quiet little horse can become fearful when things go wrong. It took me a few days of just been there for him and a few carrots on the ground for him to find near me - he is not fed by hand as my grandchildren handle him. Took about a week to make him cuddly and secure again but even now he doesn't like my hand going near that eye to brush the chaff away. He insists on putting his nose under the chaff to the bottom of his feed bin so now I am only putting a little bit of food in at a time. So it can happen to them all but patience and consistency will bring them back to us.