Short answers, pulled from the story.
The House of Commons debated the conduct of the war following the failure to stop Germany from occupying Norway. Chamberlain faced intense criticism and a vote of censure that reduced his majority to just 81 votes.
Admiral Sir Roger Keyes, Leo Amery, David Lloyd George, and Winston Churchill all delivered speeches attacking Chamberlain's leadership. Labour leader Clement Attlee also criticized government planning while defending the need for unity.
The debate occurred on Tuesday the 7th of May 1940 when the House sat at 14:45 under Speaker Edward FitzRoy. The session continued until after midnight with the final division occurring around 23:00.
Chamberlain resigned because the government lost its majority in the vote of censure held on the 7th of May 1940. Labour and Liberal parties refused to serve under him once Germany launched its western offensive on the 10th of May 1940.
The government won 281 votes against 200 but suffered a reduced majority of just 81 members. Forty-one normal supporters voted with the Opposition while another sixty Conservatives abstained deliberately.