Grim's Ditch or Grim's Dyke or Grimes Dike is a great earthwork in the London Borough of Harrow (before 1965 in Middlesex) and lends its name to the gentle escarpment it crowns, marking Hertfordshire's border. It extended east-west about from the edge of Stanmore where an elevated neighbourhood of London, Stanmore Hill, adjoins Bushey Heath to the far north of Pinner Green - Cuckoo Hill. Today the remaining earthworks start mid-way at Harrow Weald Common. It takes its name from the likely Roman Britain-era earthwork which became called one of seven Grim's Ditches, a few of which have two or three rows, in central-to-southern England.