Rearing when led

[Ecb+Doodlebug]

My Ardennes x has been with us for a year now and very recently (as in days ago) she started to rear if anyone tried to lead her by her head collar in the field and sometimes by her lead rope. I'm struggling to think of what has started this off. Although she has occasionally not liked being caught in the field, she always surrendered meekly once we got hold of her head collar and would follow me to the gate to put her lead rope on.
She's done this about 5 times now, only in her fields, and I can only think hat this is either a bout of in season behaviour or that she's wising up to the head collar grab trick. Also, sometimes it's been ears-back moody expression when she rears and sometimes in a playful way. All-in-all, she's not the kind of horse that I want anyone to be squished under. She's a lovely horse in all other respects and it's scaring my father half to death. Mum and I need some advice to overcome this before someone gets hurt.
Anything will be appreciated.

[Dustyisace]

My mare does the same but on the way in. When you get her click in front of her nose to stop her from rearing (it distracts her) and if she doesn't rear give her a treat. Keep doing this all the time. Even go into the field when you don't want her to be caught. If she starts rearing when led. Stop and wait before giving her a treat (depending if she doesn't rear of course!) If she does rear give her a smack on the nose, not too hard obviously. Pretty soon she will learn that you mean business. If other people get her in tell them to do this. Do not let kids get her until you are absolutely 100% sure its safe. Firstly, before you do this watch her in the field. If she appears to be head of the field then this is why she wont want to come in. Try to detect the problem before you start so you can do my way in a safe way. Like if she IS leader of the herd then lure her away from the horses before attempting to catch her. Hope this helped.

[Ecb+Doodlebug]

Thanks for the tips, she stopped in the end, but the idea of clicking in front of her nose is one tip I've never heard before. She lives alone actually so the idea of being in charge of her field was always going to happen, we just had to address if and when it comes to it. I agree a bop on the nose is exactly the ticket for this, and a treat of course if they're good, if the horse knows you're the dominant one then that's most of the battle won! Hope you're managing with your mare