Cowes Castle was built in 1539 as part of Henry VIII’s chain of coastal defences; others in the Solent included Yarmouth, Hurst and Calshot. The roles of Cowes Castle and its counterpart at East Cowes were to help prevent invasion of the Island (it was feared it would be occupied and used as a base for an invasion of England) and to protect the growing naval dockyard at Portsmouth. Stone from recently dissolved religious houses at Beaulieu and Quarr was used in the construction.

It was once believed that Cowes took its name from these two so-called ‘cow castles’ but the placename existed long before the castles were built. However the earlier small settlements of East and West Shamblord were on higher ground inland and it was the protection given by the castles against French raids that allowed the towns on the waterfront to develop. In the 16th century the Island was a noted haunt of pirates and the area was notorious for an occasional floating market at Meadhole (Osborne Bay) where they sold their stolen goods.

Cowes castle was a round blockhouse flanked by two rectangular wings, with a semi-circular barbican to the sea and a protective walled ditch to landward; the guns were mounted on the barbican and the roofs of the two storey main tower and one storey wings. However, an inventory of ordnance taken after Henry VIII’s death in 1547 shows that the guns on the wings and one each of the pieces on the tower and barbican were ‘not hable to serve’. In 1545 Henry had watched from Portsmouth as his flagship Mary Rose sank during a French attack at the east end of the Island, but that was to be the last major French incursion.

The castle was commanded by a Captain paid a shilling a day during Queen Elizabeth’s reign when there was also a Porter at 8d (old pence) a day and three gunners at 6d a day each. By 1774 when the Captain was Sir John Milles, late Lieutenant Governor of Jersey, the captain’s pay had risen to 10 shillings a day. Apart from his military duties the Captain of Cowes Castle had maritime responsibilities, such as boarding foreign ships and inspecting crew and cargo, and his castle was used as a lodging place for important visitors to the Island and as a prison. On Charles I’s arrival in 1647 it was full and he had to stay in a common alehouse in the town before proceeding to what was to become his imprisonment at Carisbrooke Castle. The dramatist and Poet Laureate Sir William Davenant (1606-1668), whom gossip held to be the offspring of Shakespeare, was imprisoned in Cowes Castle in 1650 before being removed to the Tower; he had been captured on his return from a mission to Virginia for Queen Henrietta Maria and was released two years later.

Several surveys show that the castle’s walls and foundations were in frequent need of repair due to the inroads of the sea and the ground on which it was built. East Cowes Castle appears to have been built on the Shrape mud and by Elizabeth’s reign was ruinous; some of the stone was used in a house at Newport and by the 17th century even the site had been lost. An inspection of Cowes Castle in 1692 recorded ‘The walls ..… are rent from top to bottom and is in great danger of falling to the ground with every cannons firing’.

The only record of the castle firing a shot in anger was during the Civil War on 12 August 1642 when Humphrey Turney, Captain of Cowes Castle, ‘in a furie with his own hand gave fire to one piece of ordnance and shot at the said ship the Lion’ which had challenged two ships bound for Portsmouth (the Navy had declared for Parliament and Col. Goring at Portsmouth for the King). Turney was arrested on the 16th, the castle garrisoned by Parliamentary forces the following day.

During the wars with France in the late 18th and early 19th centuries the Island was heavily garrisoned and the castle was armed with eleven 9-pounders. After the defeat of Napoleon in 1815 the castle’s defensive role lessened but in 1824 a Guide to the Watering Places stated that the castle ‘though useless as a place of defence, still maintains a captain, one master and five other gunners. A sentry is always on duty here but it would be difficult to point out what he has to guard unless it be the bathers clothes’. The baths, with associated bathing machines and lodging houses, occupied the site of the present Squadron lawn. The new award-winning Pavilion there, which replaced the traditional summertime marquees, was designed by Sir Thomas Croft to resemble an orangery; it was opened by the RYS Admiral, HRH Prince Philip, in 2000.

The castle was remodeled in 1716, a plan of 1725 showing that only the rear of the tower and the ends of the wings were by that date the original Henry VIII stonework. The front of the tower had been dismantled and a more domestic front with windows added and the defensive ditch had become a garden. More alterations took place later in the 18th century and in the 19th century the comforts of the castle were upgraded to sumptuous country house level when it became the maritime residence of Lord Anglesey, then Captain of Cowes Castle and a member of the Royal Yacht Squadron. Following his death in 1854, and that of his successor Lord Raglan in 1855, the Government reviewed the future of the castle and decommissioned it. It was leased, first to Lord Conyngham, then to the RYS whose old clubhouse was the site of the present Gloster apartments.

The Royal Yacht Squadron employed the architect Anthony Salvin to improve the building ‘replete with every comfort and luxury’. Salvin had trained in John Nash’s office, he was recognised as the greatest authority on medieval castles and was favoured for alterations; other castles he worked on include Carisbrooke, Alnwick and the Tower of London. He made extensive alterations to Cowes castle, greatly increasing the accommodation and adding the Platform, a Ballroom for summer use and the western tower. The members moved in in 1858 following an inspection by Prince Albert and the Prince of Wales. Salvin’s alterations did not meet with universal approval – ‘Some have compared the front to a monastery and the rear of the building to a nobleman’s mews, while others have declared it, from its irregular appearance, to resemble a discipline establishment’ wrote the Isle of Wight Observer.

Further changes took place in the 1920s but the last major building work and alterations to the Castle itself were in 1964 when the western range was adapted to accommodate the ladies who were originally only permitted to use the Squadron lawn. In 1928 the club had purchased the ballroom of Castle Rock, then owned by Rosa Lewis of Cavendish Hotel fame and now The Royal Corinthian Yacht Club, for use as a Ladies Annexe. For the 1964 alterations, the Squadron was able to acquire stone from John Nash’s East Cowes Castle, demolished in 1963, to ensure that the new work remained in keeping with the old.

The original shape of round tower, two wings and barbican is still discernible. The Solar of the 16th century is now the Morning Room and the Kitchen the Members’ Dining Room. The Conservation Survey undertaken for the Millennium advised relocation of the Chart Room (now on the first floor next door to the Library) that then occupied the area in front of the entrance doors. This has, once again, opened out the original Hall area of the tower on the ground floor.