What was the Cooper-Letwin Bill?

Yvette Cooper and Oliver Letwin proposed a private members bill in the House of Commons in March 2019, which became the European Union (Withdrawal) Act 2019 when it was passed. It was designed to ensure that ministers could not allow the UK to leave the EU with no deal without parliamentary approval: it facilitated an extension of the Article 50 period. Its provisions created an obligation for the government to table a motion to agree the length of extension the Prime Minister would seek from the EU. The government agreed an extension and the Act then lapsed.