Business as usual was a policy followed by the British government, under Prime Minister H.H. Asquith, during the early years of the First World War. Its fundamental belief was that in order to maintain a stable and functioning country, it was necessary to continue society in the same manner as before the war; in other words, that civilians should think of the war as "business as usual". The implication was that a morale-eroding change in behaviour equated to a victory for the enemy.
The term itself is attributed to Winston Churchill

Winston Churchill

Sir Winston Leonard Spencer-Churchill, was a predominantly Conservative British politician and statesman known for his leadership of the United Kingdom during the Second World War. He is widely regarded as one of the greatest wartime leaders of the century and served as Prime Minister twice...

, then a prominent "New Liberal". It is unclear whether Asquith, with whom the policy is also associated, himself supported it, or whether he merely felt obliged to. Certainly, he described it as "a detestable doctrine" in his memoirs.