London Coal Duty Marker on County Boundary Where Road Meets Potter Street Hill is a Grade II listed building in the Three Rivers local planning authority area, England. First listed on 3 October 1985. Marker.

London Coal Duty Marker on County Boundary Where Road Meets Potter Street Hill

WRENN ID
scarred-merlon-primrose
Grade
II
Local Planning Authority
Three Rivers
Constituency
South West Hertfordshire MP: Mr Gagan Mohindra (Con)
Country
England
Date first listed
3 October 1985
Type
Marker
Address
London Coal Duty Marker on County Boundary Where Road Meets Potter Street Hill, Sandy Lane, Harrow
OS grid reference
TQ 106 916
Coordinates
51.61319, -0.40396
Source
Historic England listing

Also on this page: flood risk · radon risk · weather exposure · detailed attributes ↓

Description

The London Coal Duty Marker is located on the county boundary where the road meets Potter Street Hill in Northwood. This marker dates from 1861 and was cast by Henry Grissell at the Regents Canal Ironworks. It is a square cast iron pier that stands one and a half metres high and is painted white. The marker features chamfered corners and a pyramid top. The City of London crest is displayed on the necking, and there is a raised panel on the front face of the shaft with the raised lettering 'Act 24 and 25 Vict. Cap 42'. The marker is partially buried and indicates the extent of the coal duty to the boundary of the Metropolitan Police District.

Local climate

London Coal Duty Marker on County Boundary Where Road Meets Potter Street Hill sits in one of the driest parts of the UK, with an average of 700 mm of rain a year. This makes it drier than 93% of listed buildings in the UK. Its exposure to wind-driven rain is lower than that of 91% of listed buildings.

It experiences an average of 30 freeze-thaw cycles a year, fewer than 65% of listed buildings. Of these, 13 follow at least 1 mm of rain in the preceding 48 hours. Average temperatures at this location have risen by 0.3°C per decade since 1991.

Averages for 1991–2020; temperature trend 1991–2025. Figures describe the wider area (a grid cell of roughly 10 km), not the individual site. Contains modified Copernicus Climate Change Service information 2026.

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