Beaumaris is a small town on the island of Anglesey of the Menai Strait . The Royal Borough of Beaumaris is the former county town of the island of Anglesey , Wales , and is located in the commote of Dindaethwy ( and historic rural deanery of Tindaethwy ) on the shore of the eastern entrance to the Menai Strait , the tidal waterway separating Anglesey from the coast of North Wales .