The other Home Guard tasked with suicide missions to disrupt the Nazis

Sitting in his kitchen in the village of Mabe in Cornwall, 16-year-old Ken Welch watched his father pull on his boots, preparing to head out into the freezing darkness of a December night. Redvers Kitchener MacDonald Welch was a granite polisher at the nearby quarry. A physically imposing man known as Don Redvers had been called into the military in the early part of the war, but had returned home after just a few days of training.

Quite why he had come home so abruptly and why his dad kept disappearing at night and on weekends left Ken with several burning questions. But, aware his father was unwilling to answer anything, Ken had, up until this night, left the subject well alone. All Don had ever told his wife and son was that he was part of the Home Guard, but Ken had never seen him with other members of the local unit, and certainly never in uniform.

Coupled with his disappearing act, Ken was determined to find out the truth. So that December evening, he followed his father out of the house through the country lanes for a mile until they arrived at the quarry where Don worked. Now more curious than ever, Ken broke his cover and shouted out to his dad. He knew immediately his father was less than happy to see him. Ken’s sudden appearance meant that Don now had a life-changing decision to make about his son. And as Ken later realised with shock, it could have gone very differently indeed.

Instead, Don grabbed his son, opened a hidden hatch in the ground and pulled the 16-year-old down a ladder and into a corrugated iron-lined underground structure below the surface.

Only once inside this mysterious bunker – an “operational base” as these structures were officially called – did Don explain that he was not in fact a member of the Home Guard at all. In reality, he was a member of a top-secret civilian group that, if the Germans successfully invaded Britain, would launch a suicidal bid to disrupt the enemy.

That included destroying ammunition and fuel dumps, blowing up key bridges, hitting convoys and aircraft, and assassinating German officers and British collaborators. Their life expectancy was just two weeks and, because of this short but vital window, they had been ordered to kill anyone who accidentally found their bunkers.

Luckily for Ken, his father allowed him to join the local patrol rather than adding him to the hit list.

Don was typical of the men who were picked to join the so-called Auxiliary Units. Farmers, farm workers, gamekeepers (and poachers), quarrymen, miners and others in reserved occupations who knew the countryside around them intimately.

Many, because of their occupations, knew how to handle weapons and explosives.

Ken is now 99 years old and one of the remaining, if not perhaps the last, Auxiliary Unit member left alive.

Like 90% of his comrades, he never spoke about his wartime role post-war.

Following the end of hostilities, he never even discussed it with his father and his mother died without knowing what her husband and son would have done if the Germans had taken Britain.

It has only been in the last couple of years that he has felt able to reveal this wartime service to family and friends

Now a new documentary on Dan Snow’s streaming service, History Hit, explores this remarkable group and other British civilian units that have remained almost entirely below the radar for more than 80 years.

Working with members of the Coleshill Auxiliary Research Team, Dan and I scoured the British countryside to find Auxiliary Unit Operational Bases that have lain undiscovered since being shut up at the end of the war. During one trip to Wales, we were able to unearth a bunker that a local patrol had created from an abandoned mine in which a whole raft of wartime items remained – entombed when the men destroyed the entrance and exit in 1944.

We also travelled to Dorset where an operational base revealed much about the living conditions that these brave volunteers would have endured.

We also focused on the Special Duties Branch. This group recruited a very different type of civilian to the Auxiliary Units. The elderly, mothers, doctors, vicars, publicans and even children were active.

They were trained to spy on the German army as it passed through their town or village and report what they had seen: insignia, weapons, numbers of troops, vehicles and direction of travel.

This information would then be left at a dead-letter drop and picked up by a series of runners before ending up with a civilian wireless operator. They would radio on the message to Auxiliary Territorial Service women in secret bunkers like those occupied by the men of the Auxiliary Units. The women would pass the information on to GHQ to allow British commanders to make timely, informed decisions about any British counterattacks.

During the making of the documentary, we visited a bunker that would have been used by civilian wireless operators on the Devon/Dorset border.

It is the most remarkable structure, located underneath an outside toilet. A utility hatch in the garden contains a key which can be turned 90 degrees. This release mechanism allows you to go back to the toilet and lift the whole system up. Under it a ladder drops down into a bunker.

However, even then the mystery continues until a small hook on some shelves in the bunker is pulled. This is another release mechanism that allows a false wall to be pulled up, revealing a second, smaller chamber.

This is where the radio operator would have sat, waiting for information of the latest German troop movements.

On the outskirts of the house remains a tree stump but, like everything related to this site, it is not what it seems.

The last runner in the line of this particular cell would place the information in a split tennis ball and head to the stump.

By revolving the top of the stump, the runner could push the tennis ball down, where it would run through pipes, ending up right next to the wireless operator.

If one site sums up the level of ingenuity, determination, secrecy and bravery of these civilian groups, then it is this – it really does have to be seen to be believed.

With almost all the veterans of these groups now gone to their graves, the vast majority never having breathed a word of their secret wartime role, we enjoyed a rare opportunity to reunite a member of the Auxiliary Units with his operational base.

At stand-down in November 1944, Ken Welch and his father had shut up their base, sealing it to ensure its secrecy.

Over the years that followed Ken got on with his life, married, had children and found a career as a piano tuner.

He simply put to the back of his mind his wartime role as well as the exact location of his bunker. Only in the last couple of years have researchers been able to locate it, clean it out and make it accessible – allowing Ken to visit for the first time in 80 years.

In an emotional return, the documentary follows Ken back into the bunker where he had spent so much time with his father and his comrades of the Mabe patrol.

“It feels so strange being back, I almost can’t believe it. I was here then and I’m here again. I remember being here with my father,” he told us. “I was living every boy’s dream. It isn’t many 17-year-olds who were running around the countryside with a Tommy gun! It’s all coming back gradually. Thank you for bringing me here. Eighty years – I can’t believe it.”

For eight decades the truth behind Britain’s secret civilian army had remained virtually hidden. This was certainly not Dad’s Army, rather a brutal, suicidal effort to hinder the German occupiers who had taken control of Britain and no one was in any doubt of the dangers of discovery and death at the hands of the Gestapo. Indeed, all were prepared to make the ultimate sacrifice for the country in its hour of need.

We have a strange pride in the bumbling, chaotic, unprepared story that has rarely been told about Britain’s efforts to defy the Nazis. Now is the time for a new pride, one that sees Britain as powerful and prepared and with civilians trained to be utterly ruthless in the defence of their country.

Let’s hope we don’t need to do the same in the near future.

• Churchill’s Secret Army is available now on streaming service History Hit