The forts and defences we care for tell the stories of England's defiance of a whole range of enemies, Scots, French, Spanish, Dutch and German, over nearly five centuries. Many of them were updated again and again to face successive foes, with stronger and stronger fortifications and increasingly sophisticated weapons ranging from early cannon to Second World War anti-aircraft guns.

Unlike medieval castles, which were essentially fortified residences, these forts were purely military, and primarily designed to mount artillery to sink or drive off enemy warships and invaders. Although Dartmouth Castle was purpose-built for 'ship-killing' guns in the late 1400s, 'artillery forts' really came into their own under Henry VIII, whose chain of over 30 coastal forts built between 1539 and 1547 was the first co-ordinated scheme of national defence since Roman times. Intended to protect England's south and east coasts against the threat of invasion from Catholic Europe, they were distinctively squat and rounded, designed to deflect incoming enemy cannon balls and provide all-round firepower from their own tiers of heavy guns. We care for nearly all the surviving examples, from Pendennis Castle and St. Mawes Castle in Cornwall via Portland Castle in Dorset and Yarmouth Castle on the Solent to Walmer Castle and Gardens and Deal Castle in Kent, among the earliest and most elaborate of them all.

By the time England faced a fresh threat from the Spanish Armada in 1588, military technology had moved on. Circuits of new-style 'angled bastions', giving the maximum field of fire from the fewest guns, were hurriedly built to reinforce old fortresses like Carisbrooke Castle, and also survive impressively complete around Berwick-upon Tweed Castle and Ramparts. The same style was adopted for Tilbury Fort, erected to defend the Thames Estuary after the Dutch shocked England in 1667 by burning her fleet at anchor near Upnor Castl

In the years around 1800, England's defences were strengthened against a serious threat from Napoleon's France. Dover Western Heights were built to protect Dover Castle, which housed an underground barracks for 2,000 soldiers, and we also care for Dymchurch Martello Tower, one of over 100 little single-cannon forts protecting vulnerable beaches between Sussex and Suffolk. France was feared again in the 1850s and 1860s, by which time the development of vastly more powerful guns necessitated a complete revamp, at enormous cost, of Britain's defences. Largely unaltered Fort Brockhurst, one of many new forts, was built at the same time to help protect Portsmouth harbour.

The most dangerous threat of all came in 1940, when Britain was menaced from land, sea and air by a powerful German enemy just across the Channel. Many existing forts and defences had been updated during the First World War, and now very many more, from Tynemouth Priory and Castle to Pendennis Castle, were again pressed into service, with new anti-aircraft guns and even a 'pillbox' disguised among the Roman walls of Pevensey Castle. Yet probably the best place to experience the atmosphere of Britain's Second World War defences are the Secret Wartime Tunnels beneath the ancient 'key to England', Dover Castle.