La Rocco Tower was built between 1796 and 1801 and it derives its name from La Rocque Ho or Rocque Hou, meaning rocky islet. It was one of 30 coastal towers proposed by Sir Henry Seymour Conway when he was appointed Governor of Jersey. A programme of construction of round towers around the coast of Jersey began in 1778, but it was not until the French later threatened invasion from St Malo in 1794 that serious consideration was given to building a coastal tower at La Rocco to guard the southern end of St Ouen’s Bay.
La Rocco was the 23rd and last coastal tower in Jersey to be built following the Conway design and was also the largest and most heavily armed of the whole series. It maintained a military role into the mid-19th century, as evidenced by a Royal Engineers report in January 1848, which records that La Rocco Tower and Battery (as it had by then become known) was armed with five 32-pounder guns.
The Tower’s military role declined in the second half of the 19th century until in 1896 La Rocco Tower and Battery was included in a list of War Department properties identified as available for disposal through cession or sale. The States of Jersey eventually bought the site from the Crown in 1923 for £100, for the purpose of providing a landmark for shipping (although there is no evidence that it was ever used as such).
During World War Two, St. Ouen’s Bay was considered as the most likely beach for an Allied landing. The German occupying forces constructed a large number of defensive structures throughout the area, including the modification and reuse of earlier fortifications, whose strategic position and robustness of construction again proved to be of military value. The Germans adapted La Rocco Tower and installed landmines around the Tower for use against the Allies, the explosives being wired to Le Braye slipway. The accidental detonation of some of these landmines in 1943 inflicted damage to the Tower, particularly the loss of parts of the projecting machicolations and the breaching of the southern part of the gun platform (it is most likely that this damage was caused by an accidental explosion rather than being the result of deliberate target practice by German artillery as is a commonly held belief). The expelled granite masonry is still strewn over the surrounding shale reef to this day.
The physical condition of the Tower deteriorated steadily in the following decades and in the late 1960s there was a public appeal to protect the building. The La Rocco Tower Appeal Committee raised funds to carry out repairs and works began on 5th May 1969.