England–Wales border point. In 926, Edward's successor Athelstan, "King of the English", summoned the Welsh kings including Hywel Dda of Deheubarth to a meeting at Hereford, and according to William of Malmesbury laid down the boundary between England and Wales, particularly the disputed southern stretch where he specified that the eastern bank of the Wye should form the boundary. By the mid-eleventh century, most of Wales had become united under the king of Gwynedd, Gruffudd ap Llywelyn. In 1055, he marched on Hereford and sacked the city. He also seized Morgannwg and the Kingdom of Gwent, together with substantial territories east of
Wales vessels lost and an average loss of life of about 78 sailors per year. Wartime action caused losses near Holyhead, Milford Haven and Swansea. Because of offshore rocks and unlit islands, Anglesey and Pembrokeshire are still notorious for shipwrecks, most notably the "Sea Empress" oil spill in 1996. 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