Anglesey the island. The highest six are Holyhead Mountain, ; Mynydd Bodafon, ; Mynydd Llaneilian, ; Mynydd y Garn, ; Bwrdd Arthur, ; and Mynydd Llwydiarth, . To the south and south-east the island is separated from the Welsh mainland by the Menai Strait, which at its narrowest point is about wide. In all other directions the island is surrounded by the Irish Sea. It is the 51st largest island in Europe, and just five square kilometres smaller than Singapore. There are several small towns scattered around the island, making it quite evenly populated. The largest are Holyhead, Llangefni, Benllech, Menai
Port of Holyhead trade war with the newly established Republic of Ireland had an adverse effect on the level of use of the port, which caused widespread unemployment in the town of Holyhead. During the Second World War, however, the Royal Dutch Navy began using the port as a base. In June 1939, the Royal Navy submarine "HMS Thetis" sank during sea trials in Liverpool Bay and it was subsequently brought to the harbour at Holyhead after being beached at Traeth Bychan. It remained at Holyhead in dry dock while the contents were removed; fourteen of the 99 victims were buried locally. A