It was never meant to be like this.

The Northern Ireland (Executive Formation) Bill was supposed to be a straightforward, simple piece of legislation rushed through Westminster to keep things ticking over in Northern Ireland while the local parties worked out a deal to get Stormont back up and running.

It has ended up as one of the most important pieces of legislation in Northern Ireland’s history with potentially huge ramifications for the UK constitution and the political future of Europe.

Earlier this week we saw the Stella Creasy and Conor McGinn amendments that will liberalise Northern Ireland’s draconian abortion laws and introduce marriage equality to Northern Ireland if an Executive is not restored at Stormont by 21 October. While the amendments bear the name of two MPs, the victory surely belongs to the activists and campaigners who have worked tirelessly over decades to promote the rights of the LGBT+ community and advocate for access to healthcare in Northern Ireland.

Much will be written about the Creasy and McGinn amendments and their impact on human rights for people living in Northern Ireland but on Thursday another amendment was passed that means this Bill could also have a huge impact on the Brexit process.

When the Bill went to the House of Lords on 17 July, an amendment was added that said that the Government would have to update Parliament on the progress of restoring the administration at Stormont. When the Bill came back to the House of Commons the Benn-Burt amendment was added to that amendment that says that if Parliament is adjourned or prorogued (fancy word for suspended) when the Government is giving those updates, MPs will have to be recalled so they can vote on a motion.

High profile backbench MPs including Hilary Benn and Dominic Grieve have been fighting a parliamentary guerrilla war against a No-Deal Brexit and this move was their latest attempt to prevent it. The amendment won’t directly stop a No-Deal Brexit, but it will give MPs a fighting chance of stopping it.

Recently, the idea of bypassing Parliament by proroguing it has been suggested as a valid option in order to ensure that the UK leaves the EU on 31 October, with likely future PM Boris Johnson refusing to rule it out. The logic is simple. There is a clear majority in Parliament who will vote to stop a No-Deal Brexit, but MPs can’t vote against crashing out of the EU if they can’t vote. If a future PM wants a No-Deal Brexit they simply prorogue Parliament until it’s done.

The Benn-Burt Amendment is designed to try and make this harder for any future Prime Minister. It doesn’t make a No-Deal Brexit impossible, however. As Brexit Secretary Steve Barclay told the BBC’s Brexitcast on Thursday, if a Prime Minister is determined to achieve a No-Deal Brexit, Parliament will struggle to stop it. What the Benn-Burt amendment does is make sure that anti No-Deal MPs will at least have a chance to go down fighting. With the government’s wafer-thin majority, John Bercow in the chair and recent parliamentary innovations including backbenchers seizing control of the order paper, the potential showdown in the Autumn will be fascinating.

What should have been a simple piece of Northern Irish housekeeping has turned into the latest Brexit battleground for two main reasons. First, the almost total breakdown in Government discipline. High profile government ministers including the Chancellor of the Exchequer Philip Hammond defied the Government whip by abstaining instead of voting against the amendment and weren’t immediately sacked. If it wasn’t for the fact that Theresa May is in the last couple of days of her premiership and Hammond and other rebels have next to no chance of a job after the next cabinet is appointed, this would be unthinkable.

Secondly, the House of Commons hasn’t had a lot of legislation to deal with recently. Almost the entire bandwidth of this Parliament has been taken up with dealing with Brexit and since the catastrophic defeats of May’s withdrawal agreement, there isn’t much for them to be getting on with. Taking these two things together there was a perfect storm for backbenchers to use this legislation to prevent prorogation.

The Bill is now back at the House of Lords for them to vote on the amended amendment (the process is literally called ping-ponging) and is likely to pass the Lords and receive Royal Assent on Monday. When it does, it will have much more of an impact than anyone envisaged when it was first introduced.