The Isle of Grain, (OE Greon meaning gravel) is the easternmost point of the Hoo Peninsula in the unitary authority of Medway in The County of Kent. No longer an island, the Isle is almost all marshland and the Grain marshes are an important habitat for birdlife. The Isle constitutes a civil parish, which at the 2001 census had a population of 1,731.
The following extract is taken from the Topographical Dictionary of Great Britain and Ireland by John Gorton, 1833:
Graine, Isle of
A parish in the Hundred of Hoo, lathe of Aylesford, opposite to Sheppey at the mouth of the Thames; it is about long and 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 (21 km) 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 need to reach London by a less circuitous route was later to be addressed by the Thames and Medway Canal, although this plan, too, was not a success.
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 earlier times the incidence of marsh fever (Malaria) was extremely high. 1918 saw Britain's last recorded outbreak of the disease.
Yantlet Creek at the south of the Yantlet Line is 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. While the water there is without question sea due to full sea water salinity, this is mirrored in all but exceptions times on all sides off the Isle of Grain save on ebb tides coupled with the outflows of the Thames and Medway being at their peak.