I congratulate Yvette Cooper on securing the debate. I was one of the original signatories to the motion, but I had to leave that behind when I was asked to do this job of speaking for my party—I was wearing many hats at one stage.

I am sure that a lot of us have learned many things during this important debate, and that underlines what has been happening during the Brexit process. In the beginning, people did not know about or pay attention to the ins and outs. It was like a motorist who gets in a car and drives down the road happy and oblivious to the difference between a camshaft, a crankshaft and a tappet, or whatever components are in the engine, because the car works and is fine.

We now have to drill down and understand what happens at borders, which essentially do three things: tariffs, VAT checks and regulatory alignment. A customs union helps only the first of those, but it also goes some way towards helping with paperwork and rules of origin. For those who knock the idea of a customs union, I point out that there are 12 of them in the world, comprising 103 of the 193 United Nations countries. Customs unions are therefore more the norm than the abnorm.

If the UK insists on being out of the customs union and the single market, it will inevitably face barriers to trade. For those who do not believe that, a cursory glance at Google Earth will show them the barrier between Norway and Sweden, both of which are in the single market but only one of which is in the customs union. If they look at the south-east corner of the European Union between Turkey and Bulgaria, or between Turkey and Greece, they will see further barriers, because Turkey is in the customs union but not in the single market. We need to be in both.

Why are we trying to do this? We have seen analysis by the Scottish Government, which was dismissed as politicking; by the Treasury, which was dismissed as mere forecasts; and by the Irish Government, which was met with silence. Analysis shows that the damage to GDP will be 2%, 6% or 8%. To give an idea of what that means, the crash of 2008 was a 2% event for GDP. Mr Clarke said that such things had not happened deliberately in the past. He was, I think, hinting that this is being done very deliberately—damage is being done to the UK economy in the full knowledge of what will happen.

The Prime Minister has not chosen the option of membership of the customs union and the single market outside the European Union, which would result in 2% damage. She has gone for the middle option of 6% damage, or three times the economic crash of 2008 over 12 years. We have to be absolutely certain that that is fully understood and communicated more widely among the public, because there will be much wailing and gnashing of teeth when it happens. As someone who was once poor said, “I have tried poverty and it is not very good.”

The Brexiteer line that I heard from Kate Hoey was that we are not in control of our trade, but nobody, by definition, is in control of their trade, because they have to deal with another partner. We certainly will not be in control when 27 other countries put up barriers to our goods, and we will have a lot less control over our trade at that point.

Anna Soubry made a number of excellent points. She talked about the idea of global Britain. May I let the House in on a secret? There is a thing called global Ireland, global Germany, global France, global Australia, global Argentina —everywhere, ladies and gentlemen, is global. On global Japan in particular, diplomats are going into offices explaining that they have put 40% of their investment into one basket in the EU, namely the UK, and they are very nervous indeed about what will happen to that investment. Outside the UK, global Japan has the biggest worry of all about exactly which direction the UK is taking.

In an intervention, Robert Neill gave the example of avionics and Specsavers. Who knew about these things? I knew about shellfish. People say that they want fantastic trade agreements with many other countries across the world, but lorries currently take shellfish from my constituency in the Hebrides to France or Spain on a journey that is uninterrupted by borders. If borders are put at the ro-ro facilities, the lorries’ journeys out and back will be delayed. We might get free trade with Paraguay, but there is no way that anyone could drive a heavy goods vehicle from the Outer Hebrides to Paraguay and back in a week. People sometimes lose sight of exactly what they are talking about. Trade does not happen on bits of paper. Trade happens because a person on my island, Donald Maclean, phones somebody in Spain and they make a deal between themselves. That is how trade works, but the Government are now putting themselves right in the middle of the trade that is happening between the Outer Hebrides and the continent of Europe, and that is going to be very damaging.

I get frustrated when I hear the Prime Minister, who has led the charge on this, saying that the European Court of Justice is not our court, but an external court. The ECJ is our court, your court and everybody else’s court. It is every European’s court, in fact. The idea that the UK and the EU are two separate entities is wrong as well. The UK is one of 28 members, and we have full access to the ECJ, just as everywhere else does.

We should also be mindful of the words of Simon Coveney, the Tánaiste and Irish Foreign Minister, because the moment might be approaching faster than we think. He said last week that if there was no agreement on the Irish border by June, everything could be off the table. The UK could crash out of the European Union a lot sooner than it thinks, because if the border issue is not sorted, no other issue will be sorted and there will be no deal. We know that the hard Brexiteers have abandoned the WTO idea because they have accepted a transition, but they might not get that transition. That could be a problem for them, but they have not yet woken up to it. Indeed, they might wake up to it too late, because the cliff edge is closer than we think. It has not been delayed as a result of the Prime Minister begging the European Union for two extra years but walking away with only 21 months.

It is absolutely incredible that the United Kingdom is taking the steps that it is taking. Mr Grieve has tried to shout to warn people and wake them up to the economic damage that is being done to the people who live in our islands. It will be worse for those in the north of England and in Scotland than it will be for those in London, but there is still going to be bad news for London. But I fear that people are not listening. They are on their ideological high horses, ignoring the facts that are staring them in the face. They are grabbing platitudes in the great hope that something will come up. The reality is that nothing is going to come up unless we climb down from a position of trying to square unsquareable circles. The UK is in a very difficult position of its own making. From my point of view as a Scottish National party member and a Scottish nationalist, we have to be referendum-ready in Scotland, because that is the only lifeboat I can see that could take us out of the economic calamity that the UK is about to force on itself.