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History & evidence · 1940–1944

Coleshill House.
The organisation that officially did not exist.

In the summer of 1940, after Dunkirk, Britain began training a stay-behind resistance network. The entry point was a post office in Wiltshire. The training centre was a house that appeared on no official list. The recruits were told to tell no one — not even their families.

Auxiliary Units · Special Duties Branch · Wiltshire · 1940–1944

The Auxiliary Units were formed in June 1940, in the weeks following the evacuation from Dunkirk, when invasion appeared not merely possible but probable.[1] They were organised under the direction of Colonel Colin Gubbins — later the head of the Special Operations Executive — and were designed to function as a stay-behind resistance network: small groups of men, recruited locally, trained to continue operating as saboteurs and intelligence agents behind enemy lines in the event of a successful German landing. They were to be completely deniable. They were to leave no formal record of their membership. They were expected, if discovered, to be killed.

Recruitment was conducted informally, through gamekeepers, farmers, foresters, and poachers — men who knew their local landscape intimately and could move through it without attracting attention.[2] Kent was among the highest-priority counties, its North Downs and Weald offering exactly the terrain the planners had in mind: rolling agricultural land with dense hedgerow cover, a network of sunken lanes, and a population already organised around the kind of outdoor activity that provided natural cover for an armed patrol moving at night.

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The Highworth entry point and Mrs Stranks

The induction procedure for Coleshill was designed to be both secure and deniable.[3] Recruits were told to travel to Highworth, a small market town in Wiltshire, and to present themselves at the post office at 23 High Street. The postmistress — Mrs Mabel Stranks — was the security checkpoint. She would ask for a specific phrase and, when satisfied, telephone Coleshill House on the number Highworth 85. A car would come. It would take the recruit by the most indirect route available.

Mrs Stranks ran this operation throughout the war. She knew the names of every man who passed through her post office door on this business, and she knew what they were going to be trained for. She told no one. She did not speak of her role until the final years of her life. She died in 1971, aged eighty-eight. The Auxiliary Units archive, partially declassified in the 1990s, confirms her role; the full list of those who passed through Highworth has not been published.

Documented record

What Coleshill training involved

Training at Coleshill covered close-combat techniques (under the instruction of Fairbairn and Sykes, the Shanghai-trained close-combat specialists who also trained SOE), explosives handling, night movement, signalling, and underground bunker construction and maintenance.

Each recruit was issued with a set of specific equipment appropriate to their operational brief. Those in the Special Duties Branch — the intelligence arm of the Auxiliary Units, as distinct from the operational patrols — received additional training in concealed communications devices and in the operation of hidden listening posts. What specific items were issued to individual recruits is not in any released document.

The Special Duties Branch, which is the section of the Auxiliary Units most relevant to the history documented here, was responsible for the collection and transmission of intelligence in advance of and during an enemy occupation.[4] It operated separately from the operational patrol structure and maintained its own communications network, reporting to a different command chain. Its records are among the least complete of any wartime intelligence organisation — a state of affairs that is itself consistent with the design principles under which it was established.

Coleshill House itself was demolished in 1952, following a fire. The site is now managed as a heritage landscape by the National Trust. The underground operational bases constructed across Kent and Wiltshire and the other high-priority counties have been located by archaeological survey, and several have been excavated. None of the material found in them has altered the fundamental picture of an organisation that was designed never to leave a record and largely succeeded in this aim.

References & notes
[1]The formation of the Auxiliary Units: David Lampe, The Last Ditch (Cassell, 1968) — the first published account; John Warwicker, With Britain in Mortal Danger (Cerebus Publishing, 2002) — the most comprehensive study. The official authorisation document is TNA WO 199/738.
[2]Recruitment criteria and methods: Warwicker, Britain in Mortal Danger, pp. 44–62. The preference for men with outdoor rural occupations is documented in the training manuals at TNA WO 199/738–742.
[3]The Highworth induction procedure and Mrs Stranks's role: Warwicker, Britain in Mortal Danger, pp. 88–92. Mrs Stranks gave a brief interview to a local newspaper in the early 1970s, shortly before her death; this is the only public account from her directly. Her role is confirmed in the Auxiliary Units archive at TNA WO 199/738.
[4]Special Duties Branch organisation and role: TNA WO 199/738. The Special Duties Branch is less well documented than the operational patrols; its records were kept separately and have been released in a more heavily redacted form. See also Nigel Warwick, Coleshill: Britain's Best Kept Secret (Coleshill Auxiliary Research Team, 2012).
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