The Isle of Portland is a limestone tied island, long by wide, in the English Channel. Portland is south of the resort of Weymouth, forming the southernmost point of the county of Dorset, England. A barrier beach over which runs the A354 road connects it to Chesil Beach and the mainland. Portland and Weymouth together form the borough of Weymouth and Portland. The population of Portland is 12,400.
Portland is a central part of the Jurassic Coast, a World Heritage Site on the Dorset and east Devon coast, important for its geology and landforms. Its name is used for one of the British Sea Areas, and has been exported as the name of North American and Australian towns. Portland stone, famous for its use in British and world architecture, including St Paul's Cathedral and the United Nations Headquarters, continues to be quarried.
Portland Harbour, in between Portland and Weymouth, is one of the largest man-made harbours in the world. The harbour was made by the building of stone breakwaters between 1848 and 1905. From its inception it was a Royal Navy base, and played prominent roles during the First and Second World Wars; ships of the Royal Navy and NATO countries worked up and exercised in its waters until 1995. The harbour is now a civilian port and popular recreation area, and was used for the 2012 Olympic Games.
Portland has been inhabited since at least the Mesolithic period (the Middle Stone Age)—there is archaeological evidence of Mesolithic inhabitants at the Culverwell Mesolithic Site, near Portland Bill, and of inhabitation in ages since. The Romans occupied Portland, reputedly calling it Vindelis. In 1539 King Henry VIII ordered the construction of Portland Castle for defence against attacks by the French; the castle cost £4,964. It is one of the best preserved castles from this period, and is open to the public by the custodians English Heritage.
Sir Christopher Wren, the architect and Member of Parliament for nearby Weymouth, used six million tons of white Portland limestone to rebuild destroyed parts of London after the Great Fire of London of 1666. Well-known buildings in the capital, including St Paul's Cathedral and the eastern front of Buckingham Palace feature the stone. After the First World War, a quarry was opened by The Crown Estate to provide stone for the Cenotaph in Whitehall and half a million gravestones for war cemeteries, and after the Second World War hundreds of thousands of gravestones were hewn for the fallen soldiers on the Western Front. Portland cement has nothing to do with Portland; it was named such due to its similar colour to Portland stone when mixed with lime and sand.
The Royal National Institution for the Preservation of Life from Shipwreck stationed a lifeboat at Portland in 1826, which was withdrawn in 1851. Coastal flooding has affected Portland's residents and transport for centuries—the only way off the island is along the causeway in the lee of Chesil Beach. At times of extreme floods (about every 10 years) this road link is cut by floods. The low-lying village of Chiswell used to flood on average every 5 years. Chesil Beach occasionally faces severe storms and massive waves, which have a fetch across the Atlantic Ocean. Following two severe flood events in the 1970s, Weymouth and Portland Borough Council and Wessex Water decided to investigate the structure of the beach, and possible coastal management schemes that could be built to protect Chiswell and the beach road. In the 1980s it was agreed that a scheme to protect against a one-in-five year storm would be practicable; it would reduce flood depth and duration in more severe storms. Hard engineering techniques were employed in the scheme, including a gabion beach crest running to the north of Chiswell, an extended sea wall in Chesil Cove, and a culvert running from inside the beach, underneath the beach road and into Portland Harbour, to divert flood water away from low lying areas.
At the start of the First World War, HMS Hood was sunk in the passage between the southern breakwaters to protect the harbour from torpedo and submarine attack. Portland Harbour was formed (1848–1905) by the construction of breakwaters, but before that the natural anchorage had hosted ships of the Royal Navy for more than 500 years. It was a centre for Admiralty research into asdic submarine detection and underwater weapons from 1917 to 1998; the shore base HMS Serepta was renamed HMS Osprey in 1927. During the Second World War Portland was the target of heavy bombing, although most warships had moved north as Portland was within enemy striking range across the Channel. Portland was a major embarkation point for Allied forces on D-Day in 1944. Early helicopters were stationed at Portland in 1946-1948, and in 1959 a shallow tidal flat, The Mere, was infilled, and sports fields taken to form a heliport. The station was formally commissioned as HMS Osprey, which then became the largest and busiest military helicopter station in Europe. The base was gradually improved with additional landing areas and one of England's shortest runways, at . There are still two prisons on Portland, HMP The Verne, which until 1949 was a huge Victorian military fortress, and a Young Offenders' Institution (HMYOI) on the Grove clifftop. This was the original prison built for convicts who quarried stone for the Portland Breakwaters from 1848. For a few years until 2005 Britain's only prison ship, HMP The Weare, was berthed in the harbour.
The naval base closed after the end of the Cold War in 1995, and the Royal Naval Air Station closed in 1999, although the runway remained in use for Her Majesty's Coastguard Search and Rescue flights as MRCC Portland. MRCC Portland's area of responsibility extends midway across the English Channel, and from Start Point in Devon to the Dorset/Hampshire border, covering an area of around . The 12 Search and Rescue teams in the Portland area dealt with almost 1000 incidents in 2005.