Anglesey /ˈæŋɡəlsi/ (Welsh: Ynys Môn) [ˈənɨs ˈmoːn], is an island and, as Isle of Anglesey, a county off the north west coast of Wales. Two bridges, spanning the Menai Strait, connect it to the mainland: the original Menai Suspension Bridge (carrying the A5), designed by Thomas Telford in 1826; and the more recently rebuilt Britannia Bridge (replacing the original designed by Robert Stephenson), which carries the A55 and the North Wales Coast Railway Line. Historian and author John Davies argues that it was during the tumultuous 10th century that the Norse name for Môn, Anglesey, came into existence; the name was later adopted into English after Anglo-Norman occupiers arrived to conquer the island during the Norman invasions of Gwynedd.