Ancient Monuments

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Grim's Ditch: section extending 1500yds (1370m) north east from Oxhey Lane

A Scheduled Monument in Harrow Weald, Harrow

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Latitude: 51.6216 / 51°37'17"N

Longitude: -0.3571 / 0°21'25"W

OS Eastings: 513826.518229

OS Northings: 192697.10952

OS Grid: TQ138926

Mapcode National: GBR 55.JM5

Mapcode Global: VHFST.RHKR

Entry Name: Grim's Ditch: section extending 1500yds (1370m) NE from Oxhey Lane

Scheduled Date: 11 March 1931

Source: Historic England

Source ID: 1002044

English Heritage Legacy ID: LO 63

County: Harrow

Electoral Ward/Division: Harrow Weald

Built-Up Area: Harrow

Traditional County: Middlesex

Lieutenancy Area (Ceremonial County): Greater London

Church of England Parish: All Saints Harrow Weald

Church of England Diocese: London


A 1.3km length of Grim’s Ditch running north-east from Oxhey Lane towards a telecommunications station before bearing east to New Lodge.

Source: Historic England


This record was the subject of a minor enhancement on 29 September 2014. The record has been generated from an "old county number" (OCN) scheduling record. These are monuments that were not reviewed under the Monuments Protection Programme and are some of our oldest designation records.

The monument includes a 1.3km length of Grim’s Ditch, also known as the Grim’s Dyke, a prehistoric linear boundary surviving as an earthwork and archaeological remains. It is situated on steeply sloping ground below Harrow Weald Common.

The earthwork is denoted by a bank, about 15m wide and 2m high, with a ditch to the south, about 4m wide and 1m deep. It runs in a generally straight course, ascending the slope, south-west to north-east for about 783m from Oxhey Lane, passing north of Grimswood Lodge and Weald Wood. It then gradually bears east and follows a slightly irregular course along the slope, towards New Lodge for a further 517m. The earthwork has been truncated along its length by Ass House Lane and two further roadways near Grim’s Dyke Hotel.

Partial excavation in 1979, prior to the construction of a roadway near Grim’s Dyke Hotel, uncovered Iron Age pottery sherds and a Late Iron Age or Romano-British hearth.

The Grim’s Ditch of Harrow is a linear earthwork which originally ran from west of Cuckoo Hill to Harrow Weald Common, with a possible easterly continuation in the Pear Wood earthwork. Later developments along the route have truncated or destroyed several parts of it. It consists of a large bank with a ditch on the south side and is thought to have been constructed in two phases. The bank was first built from quarried gravel, sand and clay. The ditch was then dug and some of the spoil deposited to the south. It is thought to be Iron Age in origin, although no conclusive dating evidence has been obtained by excavation. Documentary evidence shows that Grim’s Ditch was certainly in existence by 1306. The original purpose of the earthwork is uncertain but it most likely served to demarcate territorial boundaries.

Source: Historic England

Reasons for Scheduling

Linear boundaries are substantial earthwork features comprising single or multiple ditches and banks which may extend over distances varying between less than 1km to over 10km. They survive as earthworks or as linear features visible as cropmarks on aerial photographs or as a combination of both. The evidence of excavation and study of associated monuments demonstrate that their construction spans at least a millennium from the Middle Bronze Age, although they may have been re-used later. The scale of many linear boundaries has been taken to indicate that they were constructed by large social groups and were used to mark important boundaries in the landscape; their impressive scale displaying the corporate prestige of their builders. They would have been powerful symbols, often with religious associations, used to define and order the territorial holdings of those groups who constructed them. Linear earthworks are of considerable importance for the analysis of settlement and land use from the Bronze Age onwards; all well preserved examples will normally merit statutory protection.

Despite some damage and disturbance in the past, the 1.3km length of Grim’s Ditch near Harrow Weald Common survives well. It is one of the finest stretches of Grim’s Ditch and will contain archaeological and environmental information relating to the earthwork and the surrounding landscape in which the earthwork was constructed.

Source: Historic England


Greater London SMR 052160/00/00, 052473/00/00, 052474/00/00, 052566/00/00, 052567/00/00, MLO77783. NMR LINEAR23. PastScape 1043166.,

Source: Historic England

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