Defence Regulation 18B Defence Regulation 18B , often referred to as simply 18B , was the most famous of the Defence Regulations used by the British Government during the Second World War . The complete name for the rule was Regulation 18B of the Defence ( General ) Regulations 1939 . It allowed the internment of people suspected of being Nazi sympathisers . The effect of 18B was to suspend the right of affected individuals to " habeas corpus " . Preparations for war . The Defence Regulations existed in draft form , constantly revised , throughout the years between the world wars . In early 1939 it was decided that since a war might break out without warning or time to pass an Act of Parliament to bring in emergency regulations , the Regulations should be split into two codes . Code A would be needed immediately if war broke out and could be passed in peacetime , while Code B , containing more severe restrictions on civil liberties , would be brought in later . In order not to alert the public to the existence of Code B , Code A was simply numbered consecutively . Defence Regulation 18 concerned restrictions on movement of aircraft . It was originally intended that Code B would be imposed by an Order in Council , with retrospective indemnity being granted by an Act of Parliament should anyone dispute the actions of the authorities . On 24 August 1939 , after tension rose over Poland , the House of Commons was recalled from its summer recess to pass the Emergency Powers ( Defence ) Act , which gave authority to implement the Defence Regulations . Code A was brought into effect that day and Code B followed on 1 September . Enemy aliens were detained using powers under the Royal Prerogative , while 18B was used mainly for British nationals . 18B in force . The initial arrests were few and confined to those believed to be hard - core Nazis . By 14 September 1939 there were only 14 people interned under 18B . Several of these were German or Austrian by birth but had been naturalised as British subjects . The total would have been higher if William Joyce had not been tipped off by an MI5 officer ( probably Charles Maxwell - Knight ) about his impending internment , allowing him to flee to Germany . In the Commons a group of Labour and Liberal MPs attempted to have Code B annulled on 31 October 1939 , but were persuaded to withdraw their motion in favour of consultation that produced slightly amended wording . Expansion in May 1940 . The authorities dramatically revised their approach to the British far right in the late spring of 1940 . The recent rapid seizure of power in Norway by Vidkun Quisling , a politician whose career resembled that of Sir Oswald Mosley , raised the possibility of a fifth column deposing the British government . The fall of the Low Countries and the invasion of France led to fear of invasion . Then on 20 May 1940 a raid on the home of Tyler Kent , a cypher clerk at the U . S . Embassy , revealed that Kent had stolen copies of thousands of telegrams , including those from Winston Churchill to Franklin Roosevelt . Kent was an associate of Archibald Maule Ramsay , an openly anti - semitic MP . This opened the possibility that Ramsay might use parliamentary privilege to reveal the telegrams , which Churchill had not told the Cabinet about . It would also reveal Roosevelt was trying to help Churchill while proclaiming his support for neutrality in public . The Cabinet decided in favour of widespread detentions of the far right on 22 May . This required an amended version of the Regulation , known as 18B ( 1A ) . One of the first to be arrested , in the early morning of 23 May , was Sir Oswald Mosley . Others arrested later included Admiral Sir Barry Domvile and Sir Reginald Goodall . Popular reaction was strongly in favour , and one reader wrote to " The Times " to note with satisfaction that news of Mosley ' s arrest had been carried in the fifth column . By December 1940 there were more than a thousand detainees in custody . Life for 18B detainees . A person subject to 18B would be arrested without warning . Some were in the forces and were arrested while on parade . They would be taken first to police cells and then to prison . The first detainees were sent to HM Prison Wandsworth for men and HM Prison Holloway for women , but the men were later moved to HM Prison Brixton . With the expansion in numbers in 1940 came a shortage of prison accommodation , so some derelict wings of prisons ( including Stafford and Liverpool women ' s prison ) were brought back into use to house internees . Eventually it was decided to hold the internees in camps . The winter quarters of Bertram Mills ' s circus provided one camp at Ascot Racecourse , and uncompleted council housing at Huyton near Liverpool was used from March 1941 . Finally the authorities solved the accommodation problem , both for 18B internees and for interned enemy aliens by setting up camps on the Isle of Man . A new Act of Parliament , the Isle of Man ( Detention ) Act 1941 , was needed to authorise the transfer . The men stayed at Peveril Camp , Peel , and the women at Rushen Camp , Port Erin . A small number of designated leaders remained in Wandsworth Prison throughout , for greater security . In a few cases husbands and wives who had both been interned were later allowed to live together . The regime in the camps was relatively liberal . Free association was permitted and there were some entertainments , even including trips to cinemas . Legal process and challenging detention . There were two justifications for an order to intern : " acts prejudicial to the public safety " and " hostile origin or associations " . A detainee could challenge their detention by way of an appeal to an Advisory Committee headed by Norman Birkett . The committee would be presented with a statement of the reasons why detention had been proposed , drawn up by MI5 , which the detainee was not permitted to see . The Committee could recommend continued detention , release under conditions or unconditional release . The committee ' s recommendations went to the Home Secretary , who was not bound to accept them , and MI5 often lobbied him not to accept a recommendation to release . Some detainees attempted to take further action through the courts . Challenges were brought on the basis of " habeas corpus " , but refused on the grounds that the Home Secretary had taken his decision to intern on the basis of reports that had to be kept secret , and that he had reasonable cause to sign the internment orders . The most significant case was " Liversidge v . Anderson " , brought by Robert W . Liversidge who was a successful Jewish businessman and therefore a highly atypical 18B internee . He brought a civil action for damages for false imprisonment , but did not apply for " habeas corpus " . It was ultimately decided that where it is required in law that a Minister " has reasonable cause to believe " something before acting , a court can inquire into whether he really did believe it , but not into whether the things causing this belief were true . Lord Atkin wrote a dissent from this judgment . Archibald Maule Ramsay , the only MP detained , had the matter referred to the House of Commons Committee on Privileges for a ruling as to whether the detention of an MP was a breach of the Privilege of Parliament . The committee decided that it was not . Abolition of 18B Internments . Fear of immediate invasion subsided after the Battle of Britain and the number of 18B internees slowly decreased as the less harmful were let out . From a peak of about 1 , 000 in 1940 , by summer 1943 there were fewer than 500 . Oswald Mosley , who was said to be suffering from phlebitis , was released on 23 November 1943 , to a great deal of public criticism . The National Council for Civil Liberties demanded his continued imprisonment along with all other active fascists . The invasion of France on D - Day again lifted pressure and by the end of 1944 only 65 18B internees remained , most of whom were naturalised German - born citizens . By the time Adolf Hitler killed himself there were 11 and by V - E Day there was only one . 18B ceased to have effect a few days later .