 The first border between Wales and England was zonal, apart from around the River Wye, which was the first accepted boundary.Offa's Dyke was supposed to form an early distinct line but this was thwarted by Gruffudd ap Llewellyn, who reclaimed swathes of land beyond the dyke.The Act of Union of 1536 formed a linear border stretching from the mouth of the Dee to the mouth of the Wye.