The Marilyns transformed how Britain's hills are listed. Rather than judging a hill by its height, Alan Dawson ranked them by prominence — how far you must descend before you can climb anything higher — and defined a Marilyn as any hill, of any height, with at least 150 m of drop on all sides. The name is a gentle joke at the Munros' expense (Marilyn Monroe answering Hugh Munro). The idea proved hugely influential: it captures the hills that genuinely stand out, from major mountains to isolated coastal humps, and there are around 2,009 across Britain. Climbing them all is a lifetime's undertaking spanning the whole country; only the Lakeland Marilyns appear here.