In order to stay behind, we needed somewhere to stay: and by sucking up to the Sappers we had already brought into being what might very loosely be called a network of subterranean hide-outs in which not only the striking force—[myself] and about fifteen other idiots—but our far-flung, hand-picked collaborators in the Home Guard, would bide their time before emerging to wreak, in a variety of ill-defined ways, havoc among the invaders.

Peter Fleming, The Spectator 8 July 1966

That’s Peter Fleming, elder brother of the James Bond creator Ian, writing about his role in the creation of what would become the secret Auxiliary Units of wartime Britain—a resistance organization established in 1940 in anticipation of a German invasion of the British Isles.

I first found out about the Auxiliary Units in an episode of Rob Bell’s excellent television documentary series The Buildings That Fought Hitler, which explores the Second World War infrastructure that still litters the British countryside. I knew about the coastal defences and stop-lines, the radar stations and underground factories, but I’d never heard of the Auxiliary Units and their elaborate and secret underground “hideaways” (officially, Operational Bases). So Bell’s programme inspired me to track down a book devoted to their history. John Warwicker’s Churchill’s Underground Army (2013) appears to be a successor to a previous work on the same topic, With Britain In Mortal Danger (2005), which he edited.

I can’t tell you much about John Warwicker. I suspect he’s not the British graphic designer of the same name, but wonder if he might be the man who commanded the Special Branch protection team at 10 Downing Street during the 1970s, who published a memoir in 2015. Certainly the Warwicker of Churchill’s Underground Army seems to be very much acquainted with firearms, explosives and terrorist tactics.

The Auxiliary Units originated when, after the evacuation of Dunkirk, the prospect of a German invasion of Britain could not be discounted, and thoughts began to turn to how Britain might continue the war even under German occupation. Plans were quickly drawn up for the recruitment, training and equipping of a network of secret civilian resistance groups, originally called the Home Defence Organization, and formed under the auspices of Section D, the Secret Intelligence Service’s “dirty tricks” department. Such civilian resistance fighters would have no protection under the Hague Conventions, and in the event of capture would most likely be interrogated and executed.

Warwicker steers us initially through the complex and ever-shifting organizational structure of the Auxiliary Units—so complex, in fact, that ex-members of these Units (styled “Auxiliers”), have scant idea of who was actually in charge. This was, of course, important—ideally Auxiliers knew only the members of their own unit, and the “Intelligence Officer” responsible for their recruitment and orders, because the less about the organization they knew, the less they could betray under interrogation. They were also required to keep their true roles secret from family and friends, and many were given cover stories involving attachment to the Home Guard, to account for their repeated absences for training.

The Auxiliers were necessarily recruited from professions exempt from conscription—someone eligible for military service who was not visibly in service would immediately arouse suspicion and comment in the local community, a real risk to the security of the whole enterprise. Certain occupations were favoured: quarrymen and miners, for knowledge of explosives; gamekeepers for their knowledge of firearms and the local landscape … and the occasional poachers, too, who had a grasp of the importance of silence and stealth.

A chapter on Operational Bases describes the underground hideaways constructed by the Auxiliers. Initially informal, unventilated, prone to flooding and occasionally discovered by small boys, these soon become more standardized structures, equipped with elaborate counterbalanced trapdoors cover by a metal tray full of soil and turf that blended in to the local vegetation. An Auxilier wanting to gain access would alert those underground by dropping a marble down a fake mouse-hole near the trapdoor. This rolled down a buried section of gas-pipe and then clonked noisily into a biscuit tin inside the hideaway. Because of the independent operation of each Unit, and the secrecy surrounding Base locations, there is no record of where all these hideaways were built. Some are probably still out there, unvisited for seven decades.

Auxiliers were trained in “thuggery” (close-quarters combat) by Brigadier Geoffrey Beyts, using fighting techniques developed by William “Dangerous Dan” Fairbairn and Eric “Bill” Sykes, who had developed their techniques while serving with the Shanghai police, and who went on to develop the Fairbairn-Sykes Command Knife.

The sabotage and booby-trap techniques taught to the Auxiliers were collectively referred to as “scallywagging”, and Warwicker’s chapter on this topic is full of grim but fascinating detail. Scallywagging involved, among other things, a positive shed-load of explosives. Warwicker recounts the story of the Auxilier who, twenty years after the war, eventually breached the Official Secrets Act and phoned the police to report that he had 14,000 rounds of ammunition and a half-ton of explosives hidden in his milking shed, but it seemed likely that the Army had forgotten they needed to come and collect it.

Eventually, as the threat of invasion receded and the Army massed for the Invasion of France, many of the Auxiliers found themselves conscripted—some going on to serve with the Special Operations Executive.

The Auxiliers signed up for what would, for many, have been a suicide mission if a German occupation had every occurred. They also maintained a list of local people that they would be tasked with killing at the start of any German invasion, as potential collaborators or as risks to the security of the Auxiliary Units. Warwicker quotes one Auxilier on this topic:

If we had received an order to kill a collaborator, would we have done so without compunction? Yes! Without compunction.

In other words, the Auxiliers signed up for a ghastly job that was very likely to end in their own deaths—but the secrecy surrounding their existence means that they have received scant recognition in the years since the war ended.

On the face of it, it’s difficult to see why the existence of the Auxiliers should have been kept secret for so long—knowledge of their prior existence seems hardly a risk to national security. Warwicker ends the book with his own speculation on what might have made the Auxiliers fall into the category of “state secret”—one involves the infamous Operation Basalt Commando raid on Sark; the other buys wholeheartedly into the conspiracy theories that swirl around Rudolph Hess’s bizarre flight to Scotland in 1941.

I enjoyed reading this. The personalities involved in establishing “irregular warfare” are fascinating, and the British seem to have had a curiously early aptitude for dirty tricks. Warwicker’s narrative ranges widely, full of drama abroad and ingenuity at home. As well as having an insight into a part of Britain’s wartime history that has gone largely unrecognized, I now know a great deal more about rivalry between intelligence services, handling plastic explosives, covert radio transmission, and the design of “dead drops” for secret messages. So that’s bound to be useful, sometime.