An artillery castle, known as Portland Castle, situated along the northern shore of the Isle of Portland. It represents one of a pair (the other is Sandsfoot Castle) of coastal fortifications constructed during the reign of Henry VIII in order to provide protection for the sheltered waters of Weymouth Bay. The two forts are sited on opposite sides of the bay and are inter-visible. Portland Castle has a central citadel which is fan shaped in plan. The structure is composed of ashlar dressed Portland Stone producing a rounded external appearance. The citadel includes a single storey gun room facing across the Romano-British harbour. The gun room was originally roofed and has embrasures for a further battery of five guns protected by an embattled parapet. This also shielded a second battery situated on the roof of the accommodation block. To the south and south east of the citadel was an outer yard which contained two gun platforms. The construction of the fortification followed the advice of a Commission set up by Henry VIII in 1539, in response to a possible French invasion. It was thought to be have been complete by late 1540 and in service by early 1541. During the Civil War the castle was the scene of some fighting, after which it was used as an ordnance store and later a prison. During the 19th century, the citadel was occupied as a residence, when wood panelling was first added to the interior. The structure is Scheduled and Listed Grade I It is also in the care of the Secretary of State and is open to the public
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| <14> | SWX1963 - Monograph: Wheatley, Genevieve. 1994. A Teachers Handbook to Portland Castle. |
| <15> | SWX8680 - Unpublished document: Woodward, A. 1994. Site of Proposed Medical/Dental Centre, H M S Osprey, Portland, An Archaeological Evaluation and Desk-Top Study. |
| <16> | SDO17426 - Scheduling record: DCMS. 1997. Scheduled Monument Notification 1997. 25/09/1997. |
| <17> | SWX8579 - Unpublished document: Bridge, M C. 2000. Tree-ring Analysis of a Timber from Portland Castle, Castleton, Dorset. |
| <18> | SDO20559 - Monograph: English Heritage. 2000. Portland Castle, Dorset [guide]. |
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| <21> | SDO17183 - Unpublished document: Vartuca, Franco A. 2005. Portland Castle, Castletown, Dorset: programme of archaeological recording. |
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| <25> | SDO14978 - Serial: Linford, N. 2013. Portland Castle, Portland Bill, Dorset. Report on Geophysical Survey, November 2012. |
| <26> | SDO14739 - Digital archive: National Record of the Historic Environment. 451663. |