The Simms are British hills at least 600 metres high, with 30 metres of prominence. They started life as a number of separate P30m lists by Alan Dawson: Murdos, Corbett Tops and Graham Tops covering the 3000ft, 2500ft and 2000ft height bands; Hewitts covered England and Wales (also Ireland). In 2010 Alan Dawson unified them and extended the scope to include hills between 600 and 609.6m. As of 2019 there are over 2530 Simms. and 3 people have climbed them all. The Simms Hall of Fame is managed by Alan Dawson.
A Hewitt is a Hill in England, Wales or Ireland over Two Thousand feet high (610m) with a drop of 30 metres all around. Welsh, and, separately, English Hewitts are published in TACit Tables. These 2000-foot lists have numerous predecessors.