The charity caring for Shoreham's historic fort has reported what it's called an "unbelievable amount of damage" caused by vandals to the site, an officially protected monument.
One volunteer, the charity said, has "cleared three wheelbarrow loads of broken bricks" that offenders had smashed away from the foundations of the barrack block.
An appeal has gone out to the public, to check for any further broken bricks at the fort.
The trustees request reports about such sightings are made to Sussex Police 101 line, or by email.
According to the charity, the official status of Shoreham Fort as a Scheduled Ancient Monument means it is in the same category as the likes of Stonehenge.
They said that repairs, therefore, are a complex process in which historical authenticity must be maintained — damage cannot be easily patched-up without complex checks being made.
The Sussex Police crime reference number for reports is 1343 of 07/06/21.
About Shoreham Fort
The charity said work began on the fort early in the year of 1857 and by the June of the same year the fort was completed.
The fort was designed to position six muzzle-loaded guns.
The emplacements stood about 15 ft (4.6m) above sea level, so the visibility over the harbour entrance and neighbouring beaches would be increased, increasing the defence of the fort.
The underground magazines were each designed to take 126 barrels of gunpowder and the water tanks carried 11,578 gallons.
The fort was built to accommodate two Officers, one Master Gunner and 35 NCOs and Privates all housed in the barracks.
Manning of the fort continued until at least 1896, so it accommodated military personnel for roughly 49 years and was used, without residential occupiers, for longer.
In the Second World War a battery of six-inch guns was erected on the fort, but these have since been removed and only part of the footings survive.
There was also an aiming light station constructed on the eastern side of the fort, which still survives today.
The Barrack Block was variously used as a film studio and private dwelling before being demolished in 1958.
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