Homing pigeons, seen to be capable of carrying messages to the
enemy, were killed. Thousands of false accounts of suspicious 'night-signalling',
by which German spies might guide Zeppelins
or submarines towards their targets, were submitted. Le Queux's
German Spies in England: An exposure, published to favourable
reviews in February 1915, fabricated a system of German espionage
that ranged from German prostitutes around Piccadilly Circus to
'naturalised' businessmen of the highest social standing. Such claims
inevitably encouraged anti-German sentiments. On 13 May 1915, the
government decided to intern all 'enemy
aliens' residing in Britain for the duration of the war.
Similar, usually unfounded suspicions about German espionage activity
in Britain were raised throughout the war. Enemy agents were variously
accused of infecting cavalry horses with anthrax, starting fires
in ports and posing as circus performers or commercial travellers
to gain intelligence information.