When we look back upon this bleak and troubled time in our politics, Saturday October 19 might well go down in history as the day on which Britain finally decided just how it was going to leave the European Union; a mere three and a third years after voting to do so. Or if Sir Oliver Letwin has anything to do with it, perhaps it will just be another Saturday in October.

First it’s probably best if some context is provided. Back in September, Parliament voted in favour of the ‘Benn Act’; an act of Parliament that would have forced Boris Johnson to request an extension by October 19 if no deal had been agreed between the UK and the EU. Low and behold, on Wednesday, the Prime Minister was able to announce that a deal had in fact been reached. The new deal ditched the contentious Irish backstop and replaced it with a customs arrangement requiring customs checks on certain goods moving between Great Britain and Northern Ireland.

The new deal will be placed before the House of Commons on Saturday, the first time the Commons has sat since the invasion of the Falkland Islands in 1982. Johnson requires 320 votes to win (once you take into account the Speaker, the three Deputy Speakers and the abstentionist Sinn Fein); a tall order given that the Conservatives technically only hold 288 seats in Parliament. The DUP, the Northern Irish party allied to the Government, have already stated that they will be voting against due to the fact that, in their eyes, the new Withdrawal Agreement treats Northern Ireland differently from the other countries in the UK. This leaves three very important groups that Johnson has to win over for his deal to even stand a chance of going through.

First, the ERG. For those not entirely in tune with British politics, and who can blame you, the ERG (or European Research Group) is a group of hard Brexiteers within the Conservative Party whose sole purpose is to ensure that the Government commits to more than Brexit-in-name-only. They were a major reason why Theresa May was unable to pass her Withdrawal Agreement earlier in the year and counted the likes of Steve Baker, Mark Francois and Jacob Rees Mogg amongst their number. With Rees Mogg now in Government, the ERG’s opposition to the Government has softened somewhat although it is still a tough battle in order to prise them away from their DUP allies and make them vote for the deal.

Second, the group of twenty-one former Conservative MPs who have yet to join the Liberal Democrats and currently sit as Independent Conservatives. Their numbers include former Chancellor Phillip Hammond, former Work and Pensions Secretary Amber Rudd and London Mayoral candidate Rory Stewart. All of these MPs were expelled from the Conservative Parliamentary party in September for voting to prevent a no-deal Brexit. Having said this, most of the MPs in this group are likely to vote for the deal and did in fact vote all three times for Theresa May’s deal earlier in the year.

Finally, we come to Labour. Whilst the majority of Labour will join with colleagues from all of the other parties and vote down the deal, there are group of roughly twenty who belong to the group ‘MPs for a Deal’. They are seen as potential switches and a number have already announced that they will defy their party and vote with the Government. With the DUP against the deal, Johnson needs around 15 Labour MPs to make the long journey down the Aye corridor in order for the deal to pass.

But potentially all this might not matter. Britain’s favourite de facto Prime Minister Sir Oliver Letwin might well have once again scuppered the Government’s strategy by placing down an amendment designed to avoid any ERG shenanigans. If the amendment is successfully passed, it would mean that Johnson would have to ask the EU for an extension to Brexit even if his Withdrawal Agreement is passed by MPs on Saturday. The main worry amongst the more remain-y Tory MPs is that the ERG will vote for the deal tomorrow (ensuring that the Benn Act will never have to come into force) before switching against the deal during the big final vote shortly before October 31 and thus facilitating a no-deal, clean break Brexit slap bang on Halloween. If Letwin’s amendment is passed, the vote on the actual deal will be seen as nothing more than a meaningless show of support; that is until MPs vote on a deal again – likely to be within the next fortnight.

So despite all of the pomp and drama swirling around Westminster this Saturday, it may not in fact matter. Thanks to an outgoing independent MP named Oliver Letwin, the by-now battered and dented can will be kicked down the road yet again.