The last important domestic hurdle to Brexit has been cleared. The House of Lords has just voted to pass the European Union (Notice of Withdrawal) Bill, after the House of Commons voted to take out the amendments and to send it back to the upper house. It is likely to receive the royal assent, and become an Act of Parliament, tomorrow morning.

That means Theresa May will be ready to invoke Article 50, and to start two years of negotiation over Britain’s departure from the EU. Today, her spokesman indicated that this would probably be in the last week of this month.

It is hard to see how Brexit can be stopped now. Despite passionate arguments from Nick Clegg, accusing the Government of “sleight of hand”, and from Anna Soubry, who said – “I’m sorry I thought we lived in a democracy” – that Parliament should have a say if there is no Brexit deal, the Government got its way in the Commons. In the Lords, the debate was more subdued, with David Pannick, the crossbench peer, claiming to have won the argument about a parliamentary vote on the Brexit deal, but accepting that it was “pointless” to prolong the disagreement with the Commons.

David Davis: Government has Brexit contingency plan

The Labour leader in the House of Lords, Angela Smith, had made it clear that the official opposition would not delay the Bill further, so we are at the end of the parliamentary process – the process insisted upon by the Supreme Court. That process has given everyone the chance to have their say – in Lord Heseltine’s case at the price of losing his five government advisory posts – but it has made no difference to the outcome, which is that the Prime Minister will trigger Article 50 by the end of this month anyway.

After that, the legal arguments about whether an Article 50 notice is revocable or not fall away. Politically, it is hard to see how the UK, as a nation, could change its mind. It would require, in the words of the Scottish National Party about a Scottish referendum, “clear and sustained evidence” that the wishes of the British people had changed. That is not likely to happen even if May and the other EU leaders are unable to reach agreement after two years – a nightmare prospect that exercised many MPs today. If British public opinion is to change, it would not be until some time after the UK actually leaves the EU, when the economic cost would become clearer.

Nor does it seem likely that the two parts of the Kingdom that voted to remain in the EU, Scotland and Northern Ireland, could prevent the UK as a whole leaving. Nicola Sturgeon, the Scottish First Minister, tried to throw her spanner in the Brexit works today, but May, the chief mechanic, caught it and is looking at it. The Prime Minister said that a second independence referendum would cause division and uncertainty, but she didn’t rule it out. She will continue to say that for two years, by which time the UK, including Scotland, will have left the EU.

The Scottish National Party’s only way round this obstacle would be to organise an informal referendum, which would have no legal standing. It might be embarrassing for May to try to ignore it, but she would rather be embarrassed than break up the Union.

If Scotland cannot stop Brexit, for itself let alone for the rest of the UK, Northern Ireland won’t do so either.

In the end, the only way that Brexit can be stopped now is if there are dramatic changes in the EU itself. If, for example, Marine Le Pen were to win the French presidency in May, the future of the EU would be in doubt – and even if the EU survived, the principle of free movement of workers would be at an end. It is dangerous to predict votes, but Le Pen is a long way behind any of her rivals in the second-ballot opinion polls.

Geert Wilders is unlikely to be in government in the Netherlands after its election on Wednesday, and Emmanuel Macron is likely to be the next French president. Macron is, if anything, more pro-EU than Francois Hollande. And in the German election in the autumn, which is likely to pit Angela Merkel against Martin Schulz of the Social Democrats, both candidates are committed to the EU and see its four freedoms, including free movement, as indivisible.