Lists of mountains and hills in the British Isles in England, 366 in Wales and 11 in the Channel Islands. A Simm is a mountain the British Isles that is over high and has a prominence of at least . The word comes from Six-hundred Metre Mountain. There are currently 2,754 recorded Simms in the British Isles, including 2,188 Scottish Simms, 192 English Simms, 149 Welsh Simms, 1 Isle of Man Simm, and 224 Irish Simms. By definition, all Simms are also TuMPs (see below) and most, if not all, are mountains, depending on whether 600 metres or 2,000 feet (610 m) (e.g. a ), is used as the
British Isles also taken to be part of the British Isles, even though, as islands off the coast of France, they do not form part of the archipelago. The oldest rocks in the group are in the north west of Scotland, Ireland and North Wales and are 2.7 billion years old. During the Silurian period the north-western regions collided with the south-east, which had been part of a separate continental landmass. The topography of the islands is modest in scale by global standards. Ben Nevis rises to an elevation of only , and Lough Neagh, which is notably larger than other lakes