The Isle of Grain (Old English Greon meaning gravel) is the easternmost point of the Hoo Peninsula in the district of Medway in Kent. No longer an island, the Isle is almost all marshland and the Grain marshes are a major habitat for diverse wetland birds. The Isle constitutes a civil parish, which at the 2011 census had a population of 1,648, a net decrease of 83 people in 10 years.
Extract from the Topographical Dictionary of Great Britain and Ireland by John Gorton, 1833:
"GRAINE, ISLE OF, co. Kent
"A parish in the Hundred of Hoo, lathe of Aylesford, opposite to Sheppey at the mouth of the Thames; it is about it is about three miles and a half long, and two and a half broad and is formed by Yantlet Creek running from the Medway to the Thames. The Creek was filled up, and had a road across it for 40 years until 1823, when the Lord Mayor ordered it to be again reopened, so as to give about eight feet navigation for barges at spring tide; thus saving a distance of fourteen miles into the Medway, and avoiding the danger of going round by the Nore."
The closure of the road caused considerable anger among the residents of the Island and it was later reopened. The goods route from the Medway Towns to the upper Thames Estuary was later shortened by the Thames and Medway Canal, although this route, too, has been abandoned.
In 1855, as part of military defences guarding the Thames, Grain Tower, a fort, was built. It remained in use until 1946, having been used during both World Wars.
In various warm years the incidence of "marsh fever" (malaria) was extremely high. Since the removal of livestock from marshy areas, the population of native mosquitoes has greatly declined, and Britain's last recorded outbreak of malaria was in 1918.
Yantlet Creek at the south of the Yantlet Line was the downstream limit of the City of London's ownership of the bed of the River Thames. It is marked by a London Stone beside the mouth of the creek. Its successor for navigation purposes, the Port of London Authority, also owns the river bed up to here but has navigation policing rights on a debatable area of estuary of sea to the seaside resort of Margate which is of completely normal sea salinity.