General concern about 'Fifth Columnists' in Britain, inflamed by the press and exacerbated by the invasion of Holland in May 1940, resulted in the internment of Category B aliens who had previously been subject to light restrictions.
The fall of France and Mussolini's declaration for the Axis prompted the 'Collar the lot' approach and those previously categorised C - largely refugees from Nazi oppression - were also interned.
The risk of invasion and increased internee numbers made Australia and Canada seem safer places to hold both internees and pows. Approaches were successful and Canada agreed to accept 7,000. This resulted in the transfer to Canada in June/July of some 4,000 enemy aliens with about 2,000 captured enemy combatants whose numbers were to be greatly increased by those captured in North Africa in 1942/3 and following D-Day in 1944.