On the Double Bastion section of the West Walls, 1826, a 27m tall monument to the Reverend George Walker, Joint-Governor of Derry during the Great Siege was erected. The monument was destroyed by a bomb in 1973, and replaced by a commemorative plinth in 1992. The monument lies on the outer edge of the wall, overlooking the Bogside area and St. Eugenes Cathedral. This section of the walls is the Double Bastion, so called because of a dividing wall built in 1689. It features "Roaring Meg", the largest cannon used in the Siege, donated by London Fishmongers in 1642.