Disbanded around 30 years ago, the Royal Observer Corps were Britain's early-warning system in case the country found itself being attacked with nuclear weapons.

Today, on a remote hilltop in Rushton Spencer, a major aspect of their work has been preserved and encased in concrete, in an old bunker which once formed part of a vast network.

It now operates as a museum, serving as a reminder of how men and women would've scrambled into action should the worst have happened.

The Royal Observer Corps was a unit of volunteers that spanned the length and breadth of the country.

Their duties were a continuation of those carried out by their counterparts dating all the way back to Elizabethan times, when beacon lighters would warn of invading ships.

It's for this reason that the figure of an Elizabethan beacon lighter is seen on the crest of the Royal Observer Corps, along with the motto 'Forewarned Is Forearmed'.

The motto relates to their main focus – to help alert civilians of danger so that they can flee to safety.

In 1914 the observer role was used to spot enemy aircraft flying towards London. It was then expanded to serve most parts of the country by 1939.

In 1955 the nuclear reporting role was added to the corps' duties, with the first underground bunker built in Farnham in Surrey.

This programme then continued to grow until 1963 when the whole of the UK was covered.

The purpose of each nuclear bunker was to provide protection to volunteer observers during radioactive fallout, so they could report details of nuclear blasts and fallout patterns back to headquarters.

This information could then be used for public information broadcasts, to warn local people to evacuate.

Each station had around a dozen volunteers on standby, and carried a whole host of equipment – from monitoring devices to communications gear.

It also carried rations to enable up to three volunteers to hunker down for days at a time if necessary, working shifts on rotation around the clock.

There was also a bed and chemical toilet – which would've been emptied at the same time surface duties were carried out (such as changing the filters in a pinhole camera, used to plot blast size and location.)

Civil defence cuts from 1968 saw the number of posts reduced from over 1,100 to approximately 870 – and all remaining posts were finally stood down in September 1991.

A number of members of the Rushton Spencer unit, along with like-minded people, decided to maintain their former post as a museum.

They now give guided tours of the posts, upon request, which last for around an hour at a time.

Due to the confined spaces involved, tours are restricted to small groups and there is a small charge which goes towards the cost of maintaining the post.

Visits can be arranged by contacting Dave Arnold on 01538 398 761 for details of available dates.