The Isle of Portland reaches out into the waters of the English Channel. Almost a solid block of stone, it is the most southerly point on the Dorset coast. Its greatest length from north to south is four miles and its maximum width one and a half miles, while its entire circumference is less than nine miles. The north of the island is low-lying, but half a mile inland the ground rises steeply to a maximum height of 496 feet above sea-level at the Verne. From here it slopes away gradually to the southern tip or Bill, 20 feet above sea-level. There has never been a town of Portland and the chief centres of population were originally eight hamlets. Today, three of these, Castletown, Fortuneswell and Chesil have merged to form the main settlement in the north or Underhill, as the district is called, On Tophill three more of the hamlets, Reforne, Easton and Wakeham have similarly run together. Weston and Southwell remain hamlets, while another settlement has grown up around the prison at ‘The Grove’.
The ‘Island’ is, in fact, joined to the mainland by the Chesil Beach. But since this pebble bank extends westwards for ten miles before it meets the Dorset coast at Abbotsbury and could be used as a thoroughfare only with the greatest difficulty, the term ‘island’ is no real misnomer. Between Portland and the immediate mainland to the north runs the Fleet, a narrow arm of the sea, wide enough to make the approach across Smallmouth by ferry, before the building of the modern bridge, awkward and, at times, dangerous.