drydocks in the world. The former Block Mills are of international significance, having been the first factory in the world to employ steam-powered machine tools for mass production. In 1985 a partnership between the Ministry of Defence and Portsmouth City Council created the Portsmouth Naval Base Property Trust to manage part of the historic south-west corner of the Naval Base, under a 99-year lease, as a heritage area: Portsmouth Historic Dockyard. It allows members of the public to visit important maritime attractions such as Mary Rose, and . Functioning base Portsmouth naval base is home to two-thirds of the Royal Navy's surface ships, and employs up to 17,200 people. Senior personnel The Naval Base Commander (NBC) since March 2019 Commodore Jeremy Bailey. The harbour is under the control of the King's Harbour Master (KHM), working to the Naval Base Commander is currently Commander Steve Hopper, who is the regulatory authority of the Dockyard Port of Portsmouth, an area of approximately that encompasses Portsmouth Harbour and the Eastern Solent. KHM Harbour Control is based in the Semaphore Tower building. Shipping movements are handled by a team of admiralty pilots headed by the Chief Admiralty Pilot, Nick Randall. In 1836 the Commander-in-Chief, Portsmouth was given accommodation within the Dockyard (in Admiralty House) and in 1889 he was given HMS Victory to be his ceremonial flagship. These privileges were inherited by the Commander-in-Chief Naval Home Command in 1969 and by the Second Sea Lord in 1994. The latter continued (as Commander-in-Chief Naval Home Command) to fly his flag from HMS Victory (the oldest commissioned warship in the world) until 2012. Since then, the post of Commander-in-Chief has reverted to the First Sea Lord, and with it the use of Victory as flagship. The Second Sea Lord is now at Henry Leach Building on Whale Island, which is also the headquarters of the Fleet Commander. List of based ships Ship of the line Queen Elizabeth-class aircraft carriers Type 45 destroyers – in refit – in refit Type 23 frigates (planned to transfer to HMNB Devonport) (Currently forward deployed to Bahrain for 3 years from 2022) (currently in LIFEX refit) (planned to transfer to HMNB Devonport) In changes to base porting arrangements announced in November 2017, HM Ships Westminster, Richmond, Kent and St Albans will move to the HMNB Devonport by 2023; HM Ship will move in the opposite direction. and were also to move