The Royal Navy’s strangest ship - HMS Diamond Rock

A mile off the southern coast of Martinique is a steep-sided basalt island that rises almost six hundred feet above the electric-blue waters of the Caribbean. Called Diamond Rock, it is an ancient lava plug left by a long-vanished volcano and is unoccupied by humans. But that was not always the case. The island was once home to over a hundred sailors and marines, when the island became HMS Diamond Rock - officially a sloop in the Royal Navy.

In 1803 Commodore Sir Samuel Hood was operating in the area with a small squadron. His role was to blockade Martinique, the centre of French power in the Caribbean, and in particular Port Royal, their main naval base. He was also tasked with preventing contact between Martinique and her fellow French Island to the south, St. Lucia. During 1803 there was plenty of naval action in the straights separating the islands, especially around Diamond Rock, which dominated both the approaches to Port Royal and the traffic between the islands. During quieter moments in the campaign boats from the squadron would visit the Diamond Rock to collect thick stemmed grass from which the sailors weaved themselves straw hats, and for supplies of edible plants to help ward off scurvy. Reports from these expeditions filtered back to Hood, who visited the island to reconnoitre it with his first lieutenant, James Wilkes Maurice – a keen amateur mountaineer. They were impressed with what they found.

From the summit of the island, on a clear day, a lookout could see almost forty miles in every direction - far enough to spot any French ships stirring in the area. With the construction of a simple mast, news of the enemy could be quickly signalled to Hood’s ships. The steep, mountainous sides of the rock were easy to defend against attack and there were plenty of caves for accommodation and to store supplies. Better still, large calibre naval cannon sited so high up would be able to dominate the area. Hood described the location as “an unsinkable stone-frigate” in his report on his visit. It was time to bring HMS Diamond Rock into service.

In January 1804 Hood’s men took possession of the rock and began work. There were plenty of obstacles for them to overcome. For one thing, the only landing spot was a rocky ledge on the western side which was unusable in a heavy swell. For another, there was no food or water on the island, and the rock’s residents soon found they were sharing their new home with the highly venomous fer-de-lance pit viper. An initial landing party with several weeks provisions worked to overcome these obstacles. They established the first accommodation in some dry caves, installed rope ladders to allow access to the top of the rock, and began constructing gun batteries. Huge ships cables were rigged to run between the summit of the rock and the main mast of Hood’s flagship, the 74 HMS Centaur, anchored below. Using these, guns, equipment and supplies were hauled up to the summit of the rock.

Once operational, Hood officially rated HMS Diamond Rock as a sloop of war, with Lieutenant Maurice in command. His new ‘ship’ had a mixed armament of 18 and 24 pounder guns facing in various directions, a crew of 120 sailors and marines and plentiful supplies of food and water. They were regularly resupplied from the fleet by a tender, which also brought in a herd of goats and a flock of mixed guinea fowl and chickens that were allowed to run wild on the rock to provide fresh meat. The men lived in a combination of tents and caves, and even established a small hospital. They were to stay on Diamond Rock for the next 17 months.

The Royal Navy’s newest ‘ship’ soon became an enormous nuisance to the French. Thanks to their high elevation, the guns on the rock had a considerable range, and they were able to hit almost any French shipping crossing between Martinique and St. Lucia. Unlike Hood’s other ships, HMS Diamond Rock was never blown off station or forced back to base for repairs. The French quickly realised they would have to recapture the rock somehow.

Several night attacks were attempted by soldiers in boats rowing out from Port Royal, but all ended in failure. On one occasion the rowers spent most of the hours of darkness struggling against contrary winds and a strong current. By the time they arrived at the island the sun was up, and the guns promptly opened fire on them. The exhausted crews beat a hasty retreat.

Slaves from Martinique were soon involved in a clandestine trade with the island, crossing at night to trade fruit and bananas with the garrison for rum and tobacco. On one occasion they brought news of a party of French soldiers who had arrived on an adjacent plantation under the command of a lieutenant colonel of engineers. They were surveying the heights opposite Diamond Rock for a place to establish a mortar battery with which to shell the island. One of the slaves wanted to join the Royal Navy as a volunteer. Hood accepted him into the Centaur, and gave him his first task – to guide a landing party of Royal Marines that night to find the French officer. He did well, leading them across three miles of enemy territory to the plantation house, where they surprised and captured the colonel and seventeen of his men.

In May 1805 Admiral Villeneuve arrived in Martinique with a Franco-Spanish fleet of 16 ships. Among his various orders was an instruction from Napoleon to recapture Diamond Rock. On the 16th of May an overwhelming force, including two 74s, a frigate, a corvette, a schooner and eleven gunboats surrounded the island and pounded it remorselessly over the next two weeks. HMS Diamond Rock responded in kind, sinking three of the gunboats, and damaging some of the other ships. It was probably during this bombardment that the garrison’s stone water cistern was cracked, and most of their fresh water supply was lost. On the 31st of May the French landed troops on the rock, but they were soon trapped in two caves close to the bottom, unable to advance under a withering British fire. Lieutenant Maurice continued to resist for another three days, finally surrendering on the 3rd of June when he was out of both water and ammunition. The French landing party had taken sixty casualties, the British only three.

The French destroyed all the British defences on the island, after which Admiral Villeneuve departed for Europe, having already been delayed long enough by the stubborn little rock. He would meet his destiny a few months later off Cape Trafalgar. As for the crew of HMS Diamond Rock they were soon exchanged by the French. Since the island was technically a sloop of war, Lieutenant Maurice had to stand trial for the loss of his ‘ship’. He was quickly exonerated, and was rewarded for his long resistance with promotion to command of a more mobile vessel, HMS Savage.