Action of 4 April 1808 The Action of 4 April 1808 was a naval engagement off the coast off Rota near Cadiz , Spain where Royal Naval frigates " Mercury " , " Alceste " and " Grasshopper " intercepted a large Spanish convoy protected by twenty gunboats and a train of batteries close to shore . Background . Blockade duties around Cadiz were still being carried out by the Royal Navy over two years since Trafalgar ( 1805 ) . The intention was the same as it was in 1805 to keep the Franco - Spanish fleet ' locked up ' and also to keep a watchful eye on any movements by sea and attack if necessary . These included vessels such as that under the command of Captain Murray Maxwell with his 38 - gun frigate " Alceste " , 28 - gun frigate " Mercury " , Captain James Alexander Gordon , and 18 - gun brig - sloop " Grasshopper " ( 16 carronades , 32 - pounders , and two long sixes ) , under Captain Thomas Searle Attack . 38 - gun frigate " Alceste " Captain Murray Maxwell , 28 - gun frigate Mercury , Captain James Alexander Gordon , and 18 - gun brig - sloop " Grasshopper " ( 16 carronades , 32 - pounders , and two long sixes ) , Captain Thomas Searle , lay at anchor about three miles to the north - west of the lighthouse of San - Sebastian , near Cadiz , a large convoy , under the protection of about 20 gun - boats and a numerous train of flying ' artillery on the beach , was observed coming down close along - shore from the northward . At 3 p . m . , the Spanish convoy being then abreast of the town of Rota , the " Alceste " and squadron weighed , with the wind at west - south - west , and stood in for the body of the Spanish vessels . At 4 p . m . the shot and shells from the Spanish gun - boats and batteries passing over them , the British ships opened their fire . The " Alceste " and " Mercury " devoted their principal attention to the gun boats ; while the " Grasshopper " , drawing much less water , stationed herself upon the shoal to the southward of the town and so close to the batteries , that by the grape from her carronade drove the Spaniards from their guns , and at the same time kept in check a division of gun - boats , which had come out from Cadiz to assist those engaged by the two frigates . The situation of the " Alceste " and " Mercury " was also rather critical , they having in the state of the wind , to tack every fifteen minutes close to the end of the shoal . The first Lieutenant of the " Alceste " Lieutenant Stewart intended to board the convoy with boats . Accordingly the boats of the " Alceste " with marines set off and the boats of the " Mercury " quickly followed . As they came across the convoy , the two divisions of boats , led by Lieutenant Stewart , soon boarded and brought out seven merchants , from under the very muzzles of the Spanish guns and from under the protection of the barges and pinnaces of the Franco - Spanish squadron of seven sail of the line ; which barges and pinnaces had also by that time effected their junction with the gun - boats . By early evening the action had ended and the 3 frigates set off with the captured prizes . Aftermath . Exclusive of the seven merchants captured , two of the gun - boats were destroyed , and another seven had run on shore by the fire from the two British frigates and brig . The merchants contained ship timber , gunpowder and weapons . The cost to the British was one dead and two slightly wounded on board the " Grasshopper " . The damages of the latter , however , were extremely severe , as well in hull , masts , rigging and sails . With the exception of an anchor shot away from the Mercury , the damages of the two frigates were confined to their sails and ridging .