Editing MI5 (section)

===Second World War===
One of the earliest actions of [[Winston Churchill]] on coming to power in early 1940 was to sack the agency's long-term head, [[Vernon Kell]].  He was replaced initially by the ineffective [[Oswald Allen Harker]], as Acting Director General.  Harker in turn was quickly replaced by [[David Petrie]], a [[Secret Intelligence Service]] (SIS) man, with Harker remaining as his deputy.  With the ending of the [[Battle of Britain]], and the abandonment of invasion plans (correctly reported by both SIS and the [[Bletchley Park]] [[Ultra (cryptography)|Ultra]] project), the spy scare eased, and the internment policy was gradually reversed.  This eased pressure on MI5, and allowed it to concentrate on its major wartime success, the so-called [[Double Cross System|'double-cross' system]].<ref name="Masterman">{{Cite book|last=Masterman|first=John Cecil|author-link=John Cecil Masterman|year=1972|orig-year=1945|title=The Double-Cross System in the War of 1939 to 1945|publisher=[[Australian National University Press]]|isbn=978-0-7081-0459-0}}</ref>  This was a system based on an internal memo drafted by an MI5 officer in 1936, which criticised the long-standing policy of arresting and sending to trial all enemy agents discovered by MI5.  Several had offered to defect to Britain when captured; before 1939, such requests were invariably turned down.  The memo advocated attempting to 'turn' captured agents wherever possible, and use them to mislead enemy intelligence agencies.  This suggestion was turned into a massive and well-tuned system of deception during the Second World War.<ref name="Masterman" />

Beginning with the capture of an agent named [[Arthur Owens]], codenamed 'Snow', MI5 began to offer enemy agents the chance to avoid prosecution (and thus the possibility of the death penalty) if they would work as British [[double-agent]]s.  Agents who agreed to this were supervised by MI5 in transmitting bogus 'intelligence' back to the German secret service, the [[Abwehr]].  This necessitated a large-scale organisational effort, since the information had to appear valuable but actually be misleading.  A high-level committee, the Wireless Board, was formed to provide this information.  The day-to-day operation was delegated to a sub-committee, the Twenty Committee (so called because the Roman numerals for twenty, XX, form a double cross).<ref name=Masterman/> The system was extraordinarily successful.  A post-war analysis of German intelligence records found that of the 115 or so agents targeted against Britain during the war, all but one (who committed suicide) had been successfully identified and caught, with several 'turned' to become double agents.  The system played a major part in the massive campaign of deception which preceded the [[D-Day]] landings, designed to give the Germans a false impression of the location and timings of the landings (see [[Operation Fortitude]]).<ref name=Masterman/>

While the double-cross work dealt with enemy agents sent into Britain, a smaller-scale operation run by [[Victor Rothschild, 3rd Baron Rothschild|Victor Rothschild]] targeted British citizens who wanted to help Germany.  The '[[Fifth Column (intelligence operation)|Fifth Column]]' operation saw an MI5 officer, [[Eric Roberts (spy)|Eric Roberts]], masquerade as the [[Gestapo|Gestapo's]] man in London, encouraging Nazi sympathisers to pass him information about people who would be willing to help Germany in the event of invasion.  When his recruits began bringing in intelligence, he promised to pass that on to Berlin. The operation was deeply controversial within MI5, with opponents arguing that it amounted to entrapment.  By the end of the war, Roberts had identified around 500 people.  But MI5 decided not to prosecute, and instead covered the work up, even giving some of Roberts' recruits Nazi medals. They were never told the truth.<ref>{{Cite book|last=Hutton|first=Robert|date=2019|title=Agent Jack : the true story of MI5's secret Nazi hunter|publisher=Weidenfeld & Nicolson|isbn=978-1474605137|oclc=994362312}}</ref>

All foreigners entering the country were processed at the [[London Reception Centre]] (LRC) at the [[Royal Victoria Patriotic Building]], which was operated by MI5 subsection B1D; 30,000 were inspected at LRC. Captured enemy agents were taken to [[Camp 020]], [[Latchmere House]], for interrogation.  This was commanded by Colonel Robin Stephens. There was a reserve camp, Camp 020R, at [[Huntercombe (HM Prison)|Huntercombe]], which was used mainly for long term detention of prisoners.<ref>{{Cite book|first=Oliver|last=Hoare|year=2000|title=Camp 020: MI5 and the Nazi Spies — the official history of MI5's wartime interrogation centre|publisher=[[Public Record Office]]|isbn=978-1-903365-08-3}}</ref> It is believed that two MI5 officers participated in "a gentle interrogation" given to the senior Nazi [[Heinrich Himmler]] after his arrest at a military checkpoint in the northern German village of Bremervörde in May 1945.  Himmler subsequently killed himself during a medical examination by a British officer by means of a cyanide capsule that he had concealed in his mouth.  One of the MI5 officers, [[Sidney Henry Noakes]] of the [[Intelligence Corps (United Kingdom)|Intelligence Corps]], was subsequently given permission to keep Himmler's [[Suspenders|brace]]s and the forged identity document that had led to his arrest.<ref name="BBCNoakes">{{Cite web|url=https://www.BBC.co.uk/news/uk-52755565|title=Heinrich Himmler: how a fake stamp led to the Nazi SS leader's capture|website=www.BBC.co.uk|date=23 May 2020|publisher=[[BBC News]]|access-date=25 May 2020}}</ref><ref name="Mil-Intel">{{Cite web|title=Sidney Noakes Intelligence Corps officer with MI5: Himmler's false identity document|url=https://www.MilitaryIntelligenceMuseum.org/sidney-noakes|website=www.MilitaryIntelligenceMuseum.org|publisher=Military Intelligence Museum|archive-url=https://web.archive.org/web/20200525084642/https://www.militaryintelligencemuseum.org/sidney-noakes|access-date=25 May 2020|archive-date=25 May 2020|url-status=live}}</ref>