As you look out across the county's rolling green hills and sandy shorelines, it's easy to overlook one of its most enduring features - that which lies beneath the surface.

A network of tunnels runs below our feet, touching remote parts of the Thames Estuary and even the White Cliffs of Dover.

Many a story are associated with these secret passages with people once working, playing and even taking refuge in them from the threat of foreign invasion.

In Northfleet, a network of disused chalk quarry tunnels have gone largely unnoticed for the best part of two decades.

Constructed by telegraph cable company WT Henley in 1939, the twisting passages were used as an air raid shelter to shield from German bombing during the Second World War.

The tunnels were crafted into old caves within the Rosherville Gardens with at least six entrances and clear instructions emblazoned on the walls.

Each night, a mouth organist would perform as a prelude for the scores of Northfleet families who went to bed wondering whether the chalk seams would collapse above their heads.

Jean Hendy-Harris recounts growing up in the area at a time of food rationing and air raid warnings in her book Chalk Pits and Cherry Stones: A Childhood in Kent.

In the novel she recounts "the perpetual noise of the sing-songs" and the crying of the children as they took in families from the capital for a "penny for the privilege".

The tunnels survived the Blitz virtually unscathed but are now vacant and have been vandalised in recent times.

Three years ago, the developers behind Ebbsfleet Garden City looked into plans to revitalise the tunnels by linking the homes to Bluewater via the chalk cliffs.

A "cycle superhighway" was touted as a possibility giving cyclists and pedestrians direct access to the shopping centre.

But an investigation into their potential found it would be more cost effective to erect a new tunnel.

Rod LeGear is vice president of the Kent Archaeological Society and heads up Underground Kent, a research group dedicated to exploring the county's fascinating history under the surface.

As an underground surveyor, Rod has been down his fair share of holes.

In 1980, he was involved in the excavation of former chalk mine at Shepherd's Lane, Dartford, which Kent County Council, which owned the site at the time, had earmarked for a housing development.

The retired engineer recounted his experiences before an audience in Northfleet last week in which he discussed the county's Medieval chalk mines, dene holes and labyrinth of tunnels.

"The best thing that was ever taken out of Kent was chalk," he said, as it was one of the county's greatest exports and could be used for a variety of purposes from fertilising farmland to making cement.

On the topic of conservation, he said it was difficult to see what the future use of tunnels, such as those at Northfleet could be.

He identified the rise in health and safety measures nowadays, explaining how one time he was "lowered down a shaft in a JCB bucket", something quite unthinkable today.

For kids who grew up in the area, the Henley Tunnels, as they were known, were seen as a wonderful playground.

Unaware of the dangers involved, many would while away their childhoods in the underground passages, even giving them nicknames.

Air raid shelters in the form of tunnels were not unique to north Kent, however, with the largest found down the A2 in Ramsgate.

What started life as man-made railway tunnels developed into air-raid shelters and later nuclear bunkers with a capacity of up to 60,000 people.

Visitors can now get a guided tour as they follow the labyrinth of passageways which were used to protect the good folk of Ramsgate.

Just down the road in Manston is perhaps an even more intriguing set of winding passages.

They were dubbed the "Primark Tunnels" after the clothes store at Westwood Cross shopping centre was forced to shut a few years back when what appeared to be a massive sink hole appeared in the car park.

In actual fact, they had found more secret tunnels dating back to the Second World War.

Further along the coastline, one set of tunnels lays claim to having regal visitors.

The Dumpy tunnels in Dover, like those at Northfleet, are built on a former quarry site called Winchelsea Caves.

A series of tunnels were built during the First World War to test a drilling machine which was to be deployed on the Western Front.

The result proved a useful refuge for townsfolk to avoid bombing raids during the Blitz, with more than 1,300 people using it for shelter.

It is said in 1944 that even King George VI and the then Queen took refuge there when the air raid sirens sounded.

Today its upkeep is not in keeping with that of a royal and asbestos has been disturbed rending the tunnels too dangerous to enter for even Kent's most intrepid explorer.

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