Quote Originally Posted by An t-Ileach
So, it's quite likely that they all wore the leine and brat in some fashion: the leine was worn longer than it was in later times, namely to the ankle. It was probably girded with some device like a belt. I read somewhere (Ian Grimble?) that to ride one horse back, or to run when fighting, the leine was hitched up to the knee, or even above it. Could this have established a common style or wearing it, and securing the brat? It's very picturesque (Hollywood-style) to have a flowing cloak billowing out behind you, but I reckon it would be a bloody nuisance in a battle and I would expcet that most people would tie it around them so as not to snag in things - or give the enemy something to grab hold of.
Fighting in tunics:
witness Bible, "gird up your loins" meaning gather all the loose cloth and tie it in a way that doesn't interfere with your fighting.
witness Julius Ceasar: Celts fought naked.
witness Hollywood: see Ceasar add censors.
Unless the fighter is Batman, the cloth is a liability.