Do you fancy a weekend sword fight or touring a castle dressed as a laundress? Volunteers devoted to 'living history' events explain their enduring appeal A horse in colourful medieval garb ambles past, its rider heading off to the first sword fight of the day. From across the fence, music from a group of jitterbug dancers boogie-woogies through the air. And here, in a small field dotted with picnic benches, a group …