The London Stone is a stone that is said to be the place from which the Romans measured all distances in Britannia. It is now set within a stone surround and iron grill on Cannon Street, in the City of London.
Note: there is a stone obelisk one hundred yards offshore in the Thames estuary, by the Isle of Grain. This obelisk, on the east bank of Yantlet Creek, is also known as the London Stone. It indicates where the Thames becomes the North Sea, and marks the limit of the jurisdiction of the Thames Conservancy. The rest of this article is exclusively about the London Stone at Cannon Street.
