An obelisk was erected on Bréhon island in 1744 to serve as a sea mark. However the lack of visibility of the obelisk led to its replacement in 1824 by a tower 40 ft high and 34 ft in circumference, topped by a globe. During the tenure (1803-1813) of Lieutenant Governor General Sir John Doyle, there were plans to erect a guardhouse on Bréhon, but nothing came of these. Doyle was responsible, however, for substantial fortification efforts elsewhere in Guernsey, including the construction of the Martello towers of Fort Grey, Fort Saumarez, and Fort Hommet.
In the 1840s there was a renewed concern with France, with particular concern for the protection of Alderney and the other Channel Islands because of their strategic importance in the Channel. Lieutenant Governor Major-General Sir William Francis Patrick Napier proposed a number of works, including the establishment of a fort on Bréhon. In 1850 the British became concerned that the French had created fortifications at Cherbourg. This led to the construction of several towers and forts in the Channel area. The Alderney cutter Experiment was wrecked off Bréhon in March 1850. A review of Guerney's defences in 1852 recommended the construction of three artillery barracks, Fort Richmond, Fort Hommet, and Fort Le Marchant, the upgrading of Fort Doyle, and the construction of Bréhon Tower.
Work on Bréhon Tower commenced in 1854 and was completed in 1856. Bréhon Tower's role was to guard the shipping channel between Guernsey and Herm, and help protect the harbour of St Peter Port. The fort's footprint measures 65 feet by 85 feet (at the widest point), and the tower stands 34 feet high. The tower has three levels. The magazine, shell room, shifting room, stores, and fresh-water cistern were all on the ground floor. It also had latrines on the same floor, a Victorian innovation. The first floor contained the garrison's living quarters. The original plan was to put three heavy guns on the gun platform at the top, with five guns on the (second) floor below, sharing the 14 cannon ports. However, during construction the armament was cut back to three 68-pounder and two 10-inch shell guns, all on the gun platform.
By World War I the tower was obsolete and the War Office turned it over to the States of Guernsey. The garrison was originally to have consisted of two officers and 60 NCOs and other ranks, but with the reduction in armament, two officers and 30 men was deemed sufficient. During World War II, the Germans placed an anti-aircraft gun on the tower. This is credited with shooting down several allied planes, and one German plane, which crashed on Crevichon.
The Bréhon Tower is accessible only by boat.
References:Rosenborg Palace was built in the period 1606-34 as Christian IV’s summerhouse just outside the ramparts of Copenhagen. Christian IV was very fond of the palace and often stayed at the castle when he resided in Copenhagen, and it was here that he died in 1648. After his death, the palace passed to his son King Frederik III, who together with his queen, Sophie Amalie, carried out several types of modernisation.
The last king who used the place as a residence was Frederik IV, and around 1720, Rosenborg was abandoned in favor of Frederiksborg Palace.Through the 1700s, considerable art treasures were collected at Rosenborg Castle, among other things items from the estates of deceased royalty and from Christiansborg after the fire there in 1794.
Soon the idea of a museum arose, and that was realised in 1833, which is The Royal Danish Collection’s official year of establishment.