Three military-linked sites have gained protection after being added to Historic England's National Heritage List for England for 2021.
A D-class submarine, the Submarine Memorial Chapel of St Nicholas and Shoreham Memorial Cross all made a list of highlights for landmarks that have been protected in 2021.
HMS/m D1, the prototype for the D-class submarine, was the first British submarine designed for offensive operations in enemy waters – it was launched in secrecy in 1908.
Eight D class submarines were constructed, with the wreck of the HMS/m D5 submarine, lying off Lowestoft, Suffolk, protected but missing key features.
In contrast, HMS/m D1, the unique prototype for the D class submarine, is structurally sound and is in an almost complete state of preservation at Dartmouth, Devon.
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The second military-linked site on the list is the Submarine Memorial Chapel of St Nicholas, Fort Blockhouse in Hampshire.
The chapel was built in the First World War to commemorate members of the Submarine Service who lost their lives serving their country.
Fort Blockhouse is an 18th Century artillery fort and 20th Century submarine base, a location central to the defence of Portsmouth Harbour over many centuries.
It is exceptionally rare as a chapel built in England specifically to serve as a memorial to submariners – dedicated to St Nicholas, the patron saint of sailors.
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But, it is all the more significant for its location at the principal base and spiritual home of Britain's Submarine Service during the 20th Century, from where so many sailed to serve for their country.
The third and final military-linked monument is Shoreham Memorial Cross in Kent – one of only two chalk memorial crosses of its type known to survive.
The idea of Shoreham resident Samuel Cheeseman, a father who lost two sons in the First World War, it is carved into the chalk of the hillside and carefully edged with chalk blocks.
It was designed to be seen from the Shoreham War Memorial in the valley below and was carefully shaped and scaled to appear symmetrical.
Heritage Minister Nigel Huddleston, said the listings mean "we can protect our valuable heritage for future generations to learn from".
"This year's entries on to the list span the length and breadth of the country and have something to inspire everyone," he said.