British Admiralty ordered ships being in dangerous areas to extinguish all lights excluded for navigation according to the Dutch magazine Marineblad dated 1918-1919 no. 4

An item referred to the magazine Naval and Military Record dated 29 May 1918 reporting that the British Admiralty ordered that ships in the areas where a meeting with a submarine or raider of the enemy was possible all lights were to be extinguished except for the navigation lights.