River Colne, Moor Lane, Rickmansworth
In 1940 the River Colne formed part of the London Stop Line Outer (Line A), a defensive ring around the capital. Although the concept of 'stop lines' was soon dropped for a more fluid strategy of defence a chain of pillboxes and anti-tank blocks remain on the eastern bank of the river. These anti-tank blocks are in a small stream joining the River Colne beside the bridge on Moor Lane.