Formidable was lost a little over three months after the 22 September 1914 destruction of HMS Aboukir, HMS Cressy, and HMS Hogue by a single submarine. Nearly 1,500 sailors and three armoured cruisers were lost while the ships operated without destroyer escort on the North Sea blockade. The earlier disaster meant that the submarine danger was no longer an abstract possibility or a surprise first encountered off Portland. Bayly and his staff had October, November, and December in which to absorb the warning. That interval makes the decision to remain at sea without a screen an avoidable failure to adapt to evidence already available during the war.
Notable Point · 57:24-59:44
The Aboukir, Cressy, and Hogue warning before Formidable
Formidable was lost only three months after one submarine sank Aboukir, Cressy, and Hogue, making the danger of unescorted patrols impossible to treat as wholly new.