Kent coastline of Kent is continuously changing, due to tectonic uplift and coastal erosion. Until about 960, the Isle of Thanet was an island, separated by the Wantsum channel, formed around a deposit of chalk; over time, the channels silted up with alluvium. Similarly Romney Marsh and Dungeness have been formed by accumulation of alluvium. Kent's principal river, the River Medway, rises near East Grinstead in Sussex and flows eastwards to Maidstone. Here it turns north and breaks through the North Downs at Rochester, then joins the estuary of the River Thames as its final tributary near Sheerness. The Medway is
HMS Maidstone (1937) the land, entry to the jetty being guarded by sand-bagged army emplacements. "Maidstone" was also notable for a successful escape by seven Provisional IRA members on 17January 1972. The men swam close to through icy water and evaded army and police only to later hold a press conference. On 23 May 1978 "Maidstone" was broken up for scrap at the Thos W Ward scrapyard in Inverkeithing. HMS Maidstone (1937) HMS "Maidstone" was a submarine depot ship of the Royal Navy. She was built to support the increasing numbers of submarines, especially on distant stations, such as the Mediterranean and the