1. Paired with Sandsfoot Castle on the mainland, Portland provided defence for the sheltered anchorage between the island and the Chesil Bank.
When Henry VIII sought to improve coastal defence across the south of England, the Portland Roads were singled out as requiring urgent and significant fortifications; Portland Castle was the centrepiece of these defences. Seeing action in the Civil War, when the castle was seized by a successful Royalist ruse, it went onto withstand a siege.
HISTORY OF PORTLAND CASTLE
Portland Castle was one of two (the other being Sandsfoot Castle) built to protect the sheltered anchorage in the Portland Roads. One of the first wave of Henrician forts constructed due to concerns over a potential French and/or Spanish invasion, work begun in Summer 1539 and was completed by mid-1541. The design differed significantly from the contemporary forts of the 1539/40 building programme; rather than taking a completely circular shape (as was the case at Calshot or Pendennis Castles), Portland Castle was only a segment of a circle providing coverage to seaward but not inshore. Whilst the castle did have a Keep it was flanked by rectangular wings to landward.
The castle saw no action during Henry's wars nor during the Elizabethan Spanish Wars but was upgraded and re-armed during the latter conflict after a period of neglect. The castle saw action during the Civil War; initially held by Parliament it was taken by a Royalist feint in 1643. The Royalist commander dressed some of his men as Parliamentarians and used the balance of his force to chase them towards the castle. The garrison commander opened the gates to the retreating ‘Parliamentarians' at which point the castle was seized. As the adjacent anchorage was critical to the navy, which had sided with Parliament, Portland castle was besieged but with the South West under Royalist control was relieved before it could be taken. The castle finally surrendered in April 1646 when it became clear the Royalists had lost the war. The castle was subsequently used as a prison for dissenters.
Portland Castle was armed again during the Napoleonic wars but by the mid nineteenth century technical advances in artillery had made it obsolete. Coastal defence of the Portland Roads shifted to Nothe Fort, the Breakwater Fort and the Verne Citadel. Portland Castle then became the private residence for the builder of the breakwater, Captain Charles Manning.