Editing Defence Regulation 18B (section)

==Preparations for war==
The Defence Regulations existed in draft form, constantly revised, throughout the years between the world wars.{{Sfn|Simpson|1994|pp=43–47}} In early 1939 it was decided that since a war might break out without warning or without 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.{{Sfn|Simpson|1994|pp=48–49}} 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.{{Sfn|Simpson|1994|pp=47–48}}

On 24 August 1939, after tensions rose over Poland, the [[British House of Commons|House of Commons]] was recalled from its summer recess to pass the [[Emergency Powers (Defence) Act 1939|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.{{Sfn|Simpson|1994|p=50}} Enemy aliens were detained using powers under the [[royal prerogative]], while 18B was used mainly for [[British subject]]s.