Thanks Snuffy: Prances is more apt, but look at the timing of my response. I didn't spot the new verse immediately it was posted, but I reacted in less than 12 minutes. (from the original post)
Latest and best(?) (I didn't like my alternative because it tied too many lines together!)version follows.

She leaps and prances gaily
Beneath a maiden fair.
Full twenty miles she'll carry her
Of reins quite unaware

This is a Mudcat co-operative attempt (although I'm planning on putting it under Siâns & my name; but all helpers know who they are!)

Nigel