Work to repair parts of a landmark castle on the Hampshire coast has begun.
Originally built by Henry VIII to defend the coast from invasion, Hurst Castle was also used to guard the Solent during World War Two.
The £1m conservation project will repair parts of the castle added in the 20th Century.
English Heritage said it would ensure the site was "protected for the future".
Hurst Castle was originally built by Henry VIII between 1541 and 1544 to guard the Needles Passage, the narrow western entrance between the Isle of Wight and the mainland.
In the 1860s two huge wing batteries were added.
During World Wars One and Two the castle was fully garrisoned guarding the western entrance to the Solent.
The conservation project will centre on the wartime look-out tower, gun emplacements and searchlight position on top of the wing batteries.
English Heritage Properties Curator Roy Porter said: "We're looking at the concrete structures added around 1902 and also to the top of the castle in the 1940s
"These were thrown up in a hurry at a time of national emergency. Our job is to make these temporary structures permanent and protected for the future."
The castle will remain open to the public during the work. It is hoped the restoration will be finished by October.