Dylan Winter lifts the lid on a world of wartime secrets, cold war paranoia, and an age of heroic engineering.
This week he travels to Guernsey, to investigate an underground hospital built by the Nazis when they occupied the Channel Islands.
Slave labourers from across occupied Europe were brought in to hew a mile and a half of tunnels out of solid granite.
Unfortunately, in the dank underground conditions, battlefield wounds did not heal and so the hospital was converted into an ammunition store.
Now the underground complex is owned by a family of Guernsey farmers.
Dylan Winter investigates a little known slice of British military history, the Royal Observer Corps, whose members hid in little underground bunkers throughout the cold war, and waited for the atom bomb to drop. In the 1990s, the Corps was stood down, but there are still 1500 of their bunkers left. Dylan meets the veterans and tries to discover why they volunteered to bury themselves underground and wait for Armageddon.
Dylan Winter investigates the vast complex of former mine workings in Wiltshire, which during the Second World War, were used as ammunition depots and secret factories producing aircraft engines. An air of paranoia still surrounds the mines, and Dylan meets the shadowy "urban explorers" who try to penetrate their secrets.
Dylan Winter investigates a formerly Secret Nuclear Bunker in Essex, one of Britain's cold war Regional Seats of Government.
Here, in the event of a nuclear strike, civil servants in 12 "regional seats of government" would have taken over the running of Britain, meting out summary justice to surviving civilians.
Dylan tours it in the company of an anti-nuclear activist who tried to break in during the 1980s, and one of the officials who commissioned the bunker.
Was it all a massive waste of money, or could underground government really have continued with a projected 43 million dead on the surface?
Dylan Winter travels back 60 years, and down 50 feet, to discover Winston Churchill's secret wartime bunker, hidden in the North London suburb of Dollis Hill. This is where, had the war gone badly wrong, Churchill might have made his last stand against the invading Panzer brigades. After decades of neglect, this deep level bunker has recently been opened up by members of the group Subterranea Britannica, and in the company of two Sub Brit enthusiasts, Dylan goes in search of evidence of Churchill's occupation.