Henry Newman is Director of Open Europe.

Today and tomorrow’s debates in Parliament mark another crucial point in the Brexit process. For what was once known as the Great Repeal Bill – but is now more prosaically called the European Union (Withdrawal) Bill – returns to the Commons after its battering in the Lords. It’s still not clear if the Government will be able to hold off every amendment, in particular the one regarding a so-called “meaningful” vote. But the Withdrawal Bill will pass, eventually repealing the European Communities Act while providing crucial legal certainty, and taking the UK another step closer to the EU’s exit door.

Meanwhile in Brussels, events here are being followed very closely. Michel Barnier, the EU’s Brexit lead, and his team pay a great deal of attention to the minutiae of British politics, even if they occasionally misread them. Losing votes in the Commons this week would make things harder for the Prime Minister at the European Council meeting towards the end of the month. It bears repetition that probably the single biggest factor complicating Brexit negotiations is the absence of a clear Government majority and defeats rub salt into that sore.

Conversely, if the Bill passes smoothly, Theresa May will head to Brussels with the wind in her sails, as Dominic Raab eloquently put it on Sunday. Of course, many of the issues in these debates – questions of a customs union and the Single Market, for example – will be back before too long. But the Government will have demonstrated it can pass contentious bills through Parliament. Fortunately the mood music from Prime Minister’s address to the Conservative backbench 1922 Committee sounded positive.

Delivering parliamentary business without a majority is nightmarish. Before the 2015 election there were widespread predictions of a hung parliament. I was then a Cabinet Office adviser and the Civil Service spent the election period game-planning almost every scenario of coalition or supply and confidence, practically ignoring a potential Tory majority which then of course resulted. Luckily they did practice clapping a Prime Minister into Downing Street (yes!), so things were all ready for David Cameron on the morning of 8th May after his return from the Palace.

At the time I read David Steel’s A House Divided, which brilliantly captures the problems of minority governments. So no-one should envy the position of Julian Smith, the Chief Whip, who must be having to deploy all his sangfroid to keep the broad tent of the Conservative Party together. Nor that of Andrea Leadsom, the Leader of the House, who is faced with the difficult challenge of juggling the many pieces of Government legislation.

The recent decision by Labour to abstain on a Withdrawal Bill amendment to keep the UK in the Single Market is crucial. Although Labour’s alternative amendment, which seeks “full access to the internal market…with no new impediments to trade and common rights”, is basically impossible (while leaving the EU), the politics are what counts. Opposition parties can promise unicorns and not be held to account. Labour have ensured that there will be no amendment to this Bill forcing the UK to stay in the Single Market.

And last night a welcome compromise emerged from Oliver Letwin (master broker of the Cameron-era) to see off another amendment. That amendment would have required the Government to set out a statement of how it was seeking to secure a customs union with the EU. While that amendment would only bind the Government in a limited way, it would have sent an unfortunate symbol to Brussels. The Commission would see little need to engage seriously with any UK proposal on trade or the Irish border. Yesterday’s compromise – signed by a collection of MPs spanning from Nicky Morgan and Stephen Hammond on one side, to Bill Cash and Jacob Rees-Mogg on the other – firmly kicks the customs union can down the road. The issue is deferred, not resolved.

The most significant amendment still in play relates to the so-called “meaningful” vote. This is intended to put Parliament in the driving seat of the negotiations. It is constitutionally unprecedented. Some of its defenders try to argue that it should be supported because Brexit was about parliamentary sovereignty and taking back control to Parliament. But that argument rests on a misunderstanding.

Parliamentary sovereignty is the principle that Parliament is the supreme legal authority. Besides making law, Parliament is responsible for scrutinising the Government, and controlling public expenditure and taxation. But Parliamentary sovereignty does not entail making Parliament the Executive. Nor does it mean Parliament should run international affairs or direct negotiations.

But the amendment on a meaningful vote isn’t really about protecting parliamentary sovereignty any more than the Gina Miller legal challenge resulted from a preternatural interest in the use of the royal prerogative. This amendment is intended to put “no deal” out of reach of Theresa May. It would therefore limit the Government’s ability to negotiate effectively. However the amendment would have a much more profoundly damaging result than just limiting the Government’s manoeuvring space. If this amendment passes, Brussels will have every incentive to give Britain the worst possible deal and no incentive to make sensible compromises.

The Government has an extraordinarily difficult task ahead. Delivering Brexit would be hard enough in normal circumstances. The hung Parliament only adds to its complexities. Back in March 2017, MPs passed the Article 50 legislation with a large majority, giving the Government the power to start the Brexit process. It’s perfectly reasonable, and desirable, for the Commons to play an important role in Brexit – scrutinising the Government and holding them to account – but they cannot usurp the Executive’s role. It’s for the Prime Minister and her ministers to conduct the negotiations.