ground manners

Question
I recently got a horse for my daughters to ride who is an  extremely well trained english horse. I don't know much about his history, except that he is  20 something yrs old, he was a fantastic show horse, and in the last 2 yrs the boarding facility became his owner by "default", because his original owners could no longer afford board. In the last yr, he was excercised about twice a week until he was sold to me. Apparently, he is a thorougbred. He looks more like an appendix, and is extremely sensible and calm when ridden, which makes me think he may be an appendix. However, his ground manners are aweful, and at times very threatening, which makes me think that maybe his is a TB. He was here for about 2 weeks, when he decided to "threaten" me when I entered his stall. He would pin back his ears, snarl his nose and try and come at me baring his teeth. One time, I was simply walking past his stall in the evening at feeding time, and he charged at me, and the dummy wacked his front teeth on the bars! Since then, I would always carry a short crop whenever handling him.  I had to give him a whack on his neck one time when he came at me again, and he never seemed to attempt it again.  I have to lead him around with the chain over his nose all the time, otherwise, he will drag me all over, and essentially get away. On the crossties, he gets very antsy, paws, and usually puts his ears back.  He most antsy on the crossties, if he can't see is 2 pasture mates, so now, I always have them in clear view.  The positive side of this horse is, the second I get the bit in his mouth, his entire demeanor changes. My 2 daughters (11 yrs old) get on him, walk, trot, canter, do flying lead changes, etc.  Thus far, he has been PERFECT under saddle. (I've had him for 3 months now). Not once have I even felt nervous putting my beginner rider daughters on his back.  After we had him for one week, I trailered him to the dressage facility where they take lessons, and he acted like he's been there a million times.  No anxiety, no spook, no nothing. My trainer looks at me like I'm nuts when I tell her how horrible he is on the ground.  
   So, today, I got caught with my guard down.  I had all 3 of my horses in the pasture together.  I threw each of them a pile of afternoon hay.  He was eating his hay when I attempted to walk over to him. I was probably within about 5-10 feet when he took one look at me, had that "look" in his eye, pinned his ears back, threw his rump in my direction and let out a buck that landed on my hip. After the pain subsided, I wanted to beat the crap out of him, but that would get me nowhere except hurt.  When he was finished with his hay, I had the other 2 horses come into the barn, and naturally, he followed.  Came right over to me at which time I put the lead rope over his nose, crosstied him, and decided to groom him a little bit.  I didn't want him to have the last word.
I put him away at dinner time, and was able to get his blanket on him without any real problem.  He did put his ears back a little, but that was it. I'm not quite sure what his issue is, but I can assure you, he has been given nothing but pure kindness and love since he's been here. I always talk softly, and handle him in a very gentle way. I'd be lying, if I said he didn't scare the life out of me today.
 I would appreciate any advice or insight you may have.  I can also tell you that he is the lowest in the pecking order with him and my 2 mares. As of today, I keep him in his own pasture so he doesn't have to feel threatened that the others will chase him away from his hay. However, they all can play over the fence. Although he probably has some sort of issue that is making him act out this way, it is totally unacceptable behaviour, because someone will get seriously  hurt. Please help!!

Thank you,
Diane

Answer
    Hi Diane,
  The first thing I would like to say is "relax". I agree completely that his behaviour is entirely unacceptable, but it is easily understandable. Except in very rare cases, there are only two reasons why a horse would behave in the way yours has. The first one is fear. In this scenario the horse has almost certainly been very badly treated in the past, and is now defending himself. I think we would both agree that this is highly unlikely to apply in this case.
  The second (and vastly more common) cause, is the issue of who is the more dominant entity. In your case it is almost a cast iron certainty that this is the root of your problem.
  With most (if not all) animals their "personal" space is sacrosanct(this includes humans). He has invaded your space on several occasions. This is not acceptable. The dominant horse will invade the space of a subordinate on a whim, while a subordinate will never do the same unless he is about to mount a challenge for the higher ranking animals position in the hierarchy. Basically then, you have to teach your fellow that you can enter his space at any time, while he only enters yours by invitation.
  Now the question is "how do you manage this"; well there are many ways, but I normally recommend that the person arms themselves with a good stout stick ( something like the handle of a yard brush, but possibly a bit  longer). Have the stick tucked under your arm, but projecting out in front of you like a "lance". The next time you give him some hay, allow him to get through 2/3rds. or3/4ers of it, then march confidently into his paddock (armed with your weapon). Try to continue to march confidently up to him until he retreats, or your "lance", actually prods him. Try to hold him at bay for a minute or two, then you could retreat. After a minute or two you could repeat the exercise, and thereafter do it twice every feeding session.
The point of all this, is to convince him that you have the power to move him away from where he wants to be, and that he has no option but to obey.
  The issue of him dragging you around is quite easy to cure. It involves what I call "pressure and release". Put the chain over his nose as usual, and then lead him around for a bit. If you feel him putting pressure on the chain, stop walking and lock your hand and arm. Keep the resistance as long as he keeps the pressure on, but if you feel him relaxing, even the slightest bit, then you relax too. Wait about 10 seconds then walk on again. You are trying to teach him to yield to pressure, rather than to seek it. If all goes well you should be able to dispense with the chain after a day or two, but always adhere to the principle that if he applies pressure, you resist, and when he removes the pressure, you reward him by relaxing too.
  I have to confess that I am not all that happy about how my reply turned out. I thought I would be able to fly through it, but I seemed to get bogged down half way through. Before you attempt to put any of the above into practice, you might be good enough to let me know if I have made myself clear, and if you feel confident enough to go through with it.
       Slan,
           Brendan