Here is a question about this article: Public demand caused the government in October 1940 to build new deep shelters:189–190 within the Underground to hold 80,000 people but were not completed until the period of heaviest bombing had passed. By the end of 1940 significant improvements had been made in the Underground and in many other large shelters. Authorities provided stoves and bathrooms and canteen trains provided food. Tickets were issued for bunks in large shelters to reduce the amount of time spent queuing. Committees quickly formed within shelters as informal governments, and organisations such as the British Red Cross and the Salvation Army worked to improve conditions. Entertainment included concerts, films, plays and books from local libraries. 
What is the answer to this question: What year did the government start to build new deep shelters?
1940
The context mentions that the government started to build new deep shelters in October 1940.
Therefore, the answer is "1940"..