What could happen next in the Brexit saga? Here's a rundown of what turns we can expect from the process
But in the wake of the sitting – the first weekend session for 37 years – what happened then and what could happen next?
What happened yesterday in parliament?
MPs voted by a majority of 16 to back an amendment put forward by former Cabinet minister Sir Oliver Letwin to withhold approval of the deal agreed between Mr Johnson and Brussels "unless and until implementing legislation is passed".
Sir Oliver, who lost the Tory whip for voting against the Government on Brexit previously, said the amendment was "insurance" against the UK crashing out of the EU without a deal by mistake on the scheduled deadline of Thursday, October 31.
How did the Government react?
The Prime Minister decided not to have a so-called "meaningful vote" on his deal in light of the amendment.
The Government is set to bring the Withdrawal Agreement Bill - the legislation needed for Brexit - to the Commons next week.
Could Mr Johnson still get his deal through Parliament?
Yes, but time is running out before the October 31 deadline as the European Parliament would also need to ratify it.
Without a meaningful vote, support for the agreement has not yet been tested.
Though the PM has attracted support from a number of prominent Brexiteer Tories, the DUP is strongly opposed to the deal.
If there is to be another vote, when will it happen?
Jacob Rees-Mogg, the leader of the House of Commons, said the Government wants to hold another meaningful vote on Mr Johnson's deal on Monday, October 21.
The Commons Speaker, John Bercow, said he would consider whether to allow the Government's plans.
Welsh Labour MP Chris Bryant said, in a point of order, that it is not good practice for a Government to keep holding debates on the exact same subject.
If a vote does happen, one unnamed Scottish opposition MP has been quoted as saying next week will not be a simple case of the Government just winning a vote on their new deal.
"We'll amend it (over and over). It'll be totally disfigured. A different bill entirely," the MP reportedly said.
What about the letters sent last night?
Under the terms of the so-called Benn Act, which was passed against the PM's wishes, Mr Johnson was compelled to write to the EU asking for a three-month Brexit extension if he had not secured a deal by 11pm UK time on Saturday, October 19.
He told the Commons: "I will not negotiate a delay with the EU, and neither does the law compel me to do so."
But the Prime Minister did send two letters to European Council President Donald Tusk.
First, there was an unsigned photocopy of the request he was obliged to send under the Benn Act, followed by a letter explaining why the Government did not actually want an extension.
There was also an explanatory letter from Sir Tim Barrow, the UK's ambassador to the EU, which was sent to Jeppe Tranholm-Mikkelsen, the Secretary-General of the Council of the European Union.
Will the EU agree to an extension?
Despite European Commission president Jean-Claude Juncker raising doubts over another Brexit delay, the decision needs to be taken by all 27 remaining EU states, not him.
However, the EU could set a different length to an extension, either shorter or longer than the three-month one cited in the Benn Act.
The EU could decide not to formally respond to such a letter from the PM until it sees if Mr Johnson can get the Withdrawal Agreement Bill through Parliament next week.
Will there be an emergency EU summit?
If the PM gets the Withdrawal Agreement Bill through, there could be a special gathering of leaders on Monday, October 28.
If the deal needs more time at that stage to get through Parliament, leaders could agree to a short extension.