New navy dry dock for Dover according to the Dutch magazine Marineblad dated 1912-1913 no. 5

An item reported that the newly built floating dry dock for submarines by the shipyard of Swan Hunter and Wigham Richardson at Wallsend-on-Tyne arrived at Sheerness for official trials. The dock was designed by Clark and Stanfield and with a loading capacity of 1.500 ton also suitable to dock destroyers. Destined to serve at Dover.