The inscription, or explanation, on the chart makes for interesting reading 'shewing the facility by which it may be completely blockaded by four ships of war' and tells a fascinating story:
Once the British commander, Commodore Samuel Hood, decided to implement the blockade of the Island he was able to curtail the operations of privateers and intercept supplies destined for the French garrison. His next move was to fortify the rock off the southern coast of the island. Hood recognized that if the Island were fortified it would effectively allow the British to control all shipping approaching the ports on the western side of the island, as well as navigation between Martinique and its southern neighbour, St Lucia.
This chart (and the inscription), was made before the fortification of Diamond Rock was started. It talks of the benefit of the view afforded from the top of the masts of the patrolling frigates, which was estimated at 15 miles and that the view from the top of the rock was 25 miles. Once Hood, thanks to the efforts of his First Lieutenant James Wilkes Maurice, had finished the fortification (which included two 18 pounder cannons installed on the summit of the Rock, along with a garrison of 120 men) on the 7th February 1804, he wrote to the Admiralty to inform them that he had commissioned the rock as a sloop called 'Fort Diamond'.
Elsewhere on the rock the British established a hospital in one of the caves and built several more gun batteries and transformed it into a formidable bastion which was later to be a major thorn in the side of the French and the Spanish.
The chart itself is beautifully drawn and colored but it pays little attention to the topography or infrastructure of the island, presumably on the basis that there was never any intention, during this campaign, to do anything other than defend it.
See also Heritage Charts A709
