Mimmshall Brook is a 9.8 kilometres (6.1 mi)[1] long stream (brook) in Greater London and Hertfordshire, England. Rising from two sources—one in Hertsmere, Hertfordshire, and the other in Arkley, London Borough of Barnet—the brook drains into a catchment area of 52 km2 (20 sq mi) at Water End Swallow Holes, Welham Green, North Mymms. It is a tributary of the River Colne.
- ^ "HA16 Rivers and Streams" (PDF). London Biodiversity Partnership. p. 3. Retrieved 11 September 2022.