Grim's Ditch (Harrow)

Grim's Ditch (Harrow), also sometimes referred to as Grim's Dyke, is a linear earthwork in the London Borough of Harrow, England. It consists of a bank and ditch, although in many places the ditch has become infilled over time. It is thought to have been constructed in the Iron Age, potentially as a territorial boundary marker or defensive structure.

The course of the ditch is fragmented, with sections visible in various parks and open spaces around Harrow. It generally runs in a broadly west-east direction, and archaeological investigations have suggested it may have originally extended much further than its present-day visible remnants.

The name "Grim's Ditch" is common to several similar earthworks across England, and is thought to derive from the god Grim, a name often associated with the Devil or other supernatural figures, perhaps suggesting a mysterious or unknowable origin for these ancient structures.

The Harrow Grim's Ditch is a Scheduled Monument, affording it legal protection. Its remaining sections are managed and preserved to protect its archaeological and historical significance. Local historical societies and archaeological groups continue to study and document the ditch to better understand its purpose and origins.