The EU (Withdrawal) Bill returns to Parliament on Tuesday, as Theresa May resumes her bumpy journey towards Brexit. Sir Vince Cable, the Liberal Democrat leader, warns in an interview with The Independent today that, even if the bill goes through the House of Commons fairly unscathed, it is likely to be amended in the House of Lords.

Government defeats at this stage, which will probably not come before Christmas, would be insufficient to disrupt the timetable for our departure from the EU, but they would be on important questions such as overweening powers for ministers (the so-called Henry VIII clauses) and the right of Parliament to a meaningful final vote.

And the threat of a line-by-line struggle over the bnill emphasises the Prime Minister’s difficulties ahead. Before then she has to secure agreement at next month’s Brussels summit of EU leaders that “sufficient progress” has been made to move on to the next stage of the Brexit talks. That in itself is a high-stakes game, with the UK Government appearing to go backwards on all three fronts this week: on the financial settlement, reciprocal citizens’ rights and the Irish border.

Even if there is progress in December, it is fair to say that, so far, Brexit is going very, very badly. Whether this is because the Prime Minister has handled the talks badly or because the UK, as a departing member, is in an intrinsically weak position (or, more probably, both), is irrelevant. It is becoming increasingly clear that we will leave either with a bad deal or without a deal at all.

The question might then become whether or how Brexit could be softened or prevented altogether. Former prime ministers Tony Blair and Gordon Brown were quite right in recent interviews to say that now is not the time to be talking about another referendum, but that it must be open to the British people to change their minds as the implications of Brexit become clearer.

It is also interesting that Sir Vince says in his interview with us that the mood among crossbench peers – the non-aligned members of the House of Lords – appears to be shifting on the question of a “referendum on the facts”. He says: “They were asking about the basic reasoning behind it, how it would work, what the question would be.”

These are, however, questions of procedure. As is the fuss in recent days over remarks by Lord Kerr, first reported by The Independent, about the reversibility of the UK’s notification under Article 50 of its intention to withdraw. As is, indeed, the secondary fuss about whether the Government should publish its legal advice on the matter.

Before them comes a bigger question, which is that of persuasion. It is not enough for those who believe Brexit to be a bad idea to assume that people who voted to leave the EU will decide they have made a mistake when presented with the evidence of economic harm.

That evidence may seem more compelling now, but it did not persuade 17 million people in the referendum campaign and once people have voted they look for evidence that confirms they were right. Those who want to persuade their fellow citizens that the UK should at least stay in the single market, if not abandon Brexit, must think more deeply about how to make their case.

This means eschewing the polarised language of accusing others of being stupid, deluded or committing national self-harm. It means recognising that claims of present economic damage have not materialised and that claims of future damage are not believed. And it means recognising that the desire to leave the EU is not just about economics anyway.