In the 1840s it was thought that the advent of steam would make the Channel Islands more important as an advanced naval base, and also more liable to capture by the French.

Accordingly the great harbour works of Alderney were begun in 1847. Fort Clonque, the most remarkable of them, occupies a group of large rocks off the steep south-west tip of the island, commanding the passage between it and Burhou. It is reached by a causeway leading to a drawbridge entrance and was originally designed for ten 64-pounder guns in four open batteries, manned by two officers and 50 men.

Very soon, however, the further develop - ment of steam brought the Channel Islands within easy reach of mainland bases, and made another in Alderney unnecessary. In 1886 the Defence Committee recommended that Clonque, and all the other works except Fort Albert, should be disarmed but left standing.

It was thus that Hitler found them in 1940 and, imagining again that the Channel Islands had strategic value, vigorously refortified them. At Fort Clonque part of the Victorian soldiers’ quarters was replaced by an enormous casemate, housing a gun so large that its emplacement now makes a handsome bedroom looking towards Guernsey.

Most forts are of necessity large and grim, but Clonque, because it has had to be fitted to the great rocks round which it is built, is small, open and picturesque, ingeniously contrived on many levels, with stretches of grass, samphire and mesembryanthemum here and there. Any cold or damp, characteristic of such a fort, will be more than compensated for by the delight of its spectacular setting. (The clean air allows all sorts of lichen to grow on the granite walls.) On calm days the sea can be heard all round, restlessly searching the rocks; and on rough days it is comforting to reflect that the wall of the East Flank Battery is 19 feet thick. During some high tides the fort is cut off and the sea runs between it and the mainland.

The marine views are second to none: of the other islands, rocks and stacks; of two great colonies of gannets, which fish round the fort; of the lighthouses on the Casquets; and of the formidable race or current called the Swinge, which runs between Clonque and Burhou.

On all counts Fort Clonque is a most worthwhile place to have tackled, not least because when we embarked on it in 1966 military works such as this were disregarded everywhere. The rest of Alderney is also extremely pleasant; the island is just small enough to be explored entirely on foot or, very easily, by bicycle; all the Victorian and German defence works are interesting; the beaches at the north end are exceptional; and in the centre is St Anne, a very pretty little town, English with a hint of France.

Sleeps: 13