This list was the first seriously researched peakbagging list ever created, by Sir Hugh Munro in 1891. Prior to this time, detailed topographic maps for large areas were not available, so it is not surprising that the first list was made in a nation where the Ordnance Survey was ahead of the pack in creating high-quality maps.
A "Munro" is a peak in Scotland over 3000 feet high. The list has been revised many times over the years by the Scottish Mountaineering Club, and the latest revision in 1997 has 284 summits. There is a separate list of 227 "Munro Tops" with less prominence than the Munros, but there is no consistent criteria for determining if a peak is a "Top" or a full Munro.
There is no serious list of peaks in the British Isles that does not own a huge debt to Alan Dawson's The Relative Hills of Britian, the ultimate reference for the subject. The Range classification above is based on his chapter headings, with some modifications. Dawson also pioneered the use of prominence numbers to help classify peaks.