The surroundings

There are many footpaths nearby. Here is the view from 200 metres from the Reservoir.

Just half a mile away there is probably the best preserved Central Ordnance Depot in the UK although for many years an industrial estate.

Where the pipe from the reservoir arrived at the depot

The (dry) watercourse through the neighbouring wood

Not quite so dry in winter! It was used to empty the reservoir for maintenance. 

In winter

The railway that Each day  brought water to the depot before the reservoir was built

 And the other end of the tunnel