The Hunt Class Minesweepers were ordered to replace the aging Ton Class vessels and were designed principally to work in coastal and shallow water areas, such as the approaches to the River Clyde, where many of Britain's nuclear submarines are based. They are the largest warships ever constructed of Glass Reinforced Plastic (GRP) giving them the advantage of having a reduced magnetic signature whilst being strong enough to withstand shock from explosions. The ships are designed with noise reduction features to avoid accidentally triggering acoustic mines. The Hunt Class Mine Countermeasure Vessels (MCMVs) combine the roles of mine hunting and minesweeping. There are three ways they can neutralise mines: The Hunt Class also carry a small-unmanned submersible, known as the Remote Control Mine Disposal System (RCMDS), which can destroy underwater mines using explosives. Three Hunt Class vessels, Cottesmore, Brecon and Dulverton, were assigned to the Northern Ireland Squadron in 1998 to patrol the province's waterways and participate in counter terrorist operations in support of British Forces and the Royal Ulster Constabulary (RUC).