London Attractions : London Sightseeing
Ordnance Survey maps are based around the cannons located in Roy Grove, Hampton, and on the Northern Perimeter Road by Heathrow Airport five miles away.
These cannons have been used as a base line for triangulation used on all subsequent Ordnance Survey maps
OG: Hampton 1.25km
OG: Fulwell 1.38km
OG: Strawberry Hill 2.3km