Seaforth Dock (also known as the Royal Seaforth Dock) is a purpose-built dock and container terminal, on the River Mersey, England, at Seaforth, to the north of Liverpool. As part of the Port of Liverpool and Liverpool Freeport, it is operated by the Mersey Docks and Harbour Company. Situated at the northern end of the dock system, it is connected to Gladstone Dock to the south, which via its lock entrance provides maritime access to Seaforth Dock from the river. Despite planning permission having been obtained almost sixty years previously, work commenced during the 1960s on Liverpool's largest dock facility. The dock was the largest built in the United Kingdom for some time, with 10,000 ft of quay and a depth of 50 ft and world's largest lock gates.