Three Reader's Digest investigations take us into; Britain's subterranean caves, rivers, tunnels and bunkers from ancient times to the modern era; plus the shelters, secret weapons sites and hidden command centres of WW2; and the bunkers, citadels, and hidden nuclear command centres of Cold War Britain.

HIDDEN HISTORY: Be amazed by tales of Britain's hidden caves, forgotten catacombs and mysterious tunnels. Unearth the tale of Edinburgh's secret underground city and uncover the mysteries of the Hell Fire Caves. Travel beneath the City of Liverpool . Journey to Brighton's hidden network of Victorian sewers . and discover Britain's smuggling secrets scattered around our coves and coasts.

WARTIME SECRETS: From Liverpool to Dover, Westminster to Woolwich, there are hidden secrets beneath our feet. Underground hideouts that would hide a secret army - ready to attack if Germany landed troops during WW2 . The wartime bunker Churchill refused to use in North-West London . London's secret tunnels and secret stations . walkways beneath the Thames and many other bunkers and tunnels that exist under our towns and cities.

MODERN MYSTERIES: Lift the lid on Britain's Cold War bunkers. Journey deep underground to Veryan, one of the few remaining Royal Observer Corps posts . Kelvden Hatch in Essex . Corsham ammo depot and underground aircraft factory . the mysterious Pear Tree House hiding in a regular housing estate . right to the present day with a visit to a secret seed store designed to protect our crops from ecological or biological attack!