David Gauke is a former Lord Chancellor and Justice Secretary, and is MP for South West Hertfordshire.

Following Nicky Morgan’s return to the Cabinet, the Editor of this website (and my esteemed former colleague in George Osborne’s Shadow Treasury team) asked if I would like to be a regular columnist. My role, as I understood it, would be to demonstrate that all strands of Conservative Party thinking was represented on this site and, in doing so, I should therefore stir it up a bit. I gladly accepted.

It hasn’t passed my notice that my views are not entirely in harmony with the majority of ConservativeHome readers when it comes to Brexit. And, given that this article is being published at the beginning of one of the most contentious and important weeks in the Brexit saga – and I have found myself somewhat in the thick of it – this is not likely to be a gentle introduction.

Before turning to the events of the week ahead, I should say a little about the evolution of my thinking. Like most Conservatives of my generation, I came to political age in the era of Margaret Thatcher. I admired her determination to transform the British economy, her willingness to take on vested interests, her belief in the free market, free trade, sound public finances, low inflation and the need for a pro-business tax and regulatory environment.

I also shared her instincts on Europe. I was opposed to our membership of the Exchange Rate Mechanism, feared that the Delors European Commission was trying to reverse her supply-side reforms and always believed that the UK should stay outside the single currency. Throughout the 1990s and early 2000s, I feared that, in the end, we would have a choice as to whether to become part of a United States of Europe or leave the EU altogether. If it came down to that choice, I would be a Leaver.

When I entered Parliament in 2005, I joined a small group of Eurosceptics who chipped in a contribution from their Parliamentary Staffing Allowances to pay for a researcher to ensure we were ever vigilant against the advance in Euro-federalism. I even had a spell as Treasurer of this organisation, called – accurately enough – the European Research Group.

It would be fair to say that the ERG and I drifted in different directions over the years. I came to the view that the UK could be part of the EU without being destined to be part of an EU superstate.

I also came to accept that it is only possible to bring down trade barriers on the basis of co-operation with other countries. There is a trade-off between regulatory autonomy and the openness of markets and I am a free trader.

By the time we got to the 2016 referendum, I was firmly in the Remain side. Not a starry-eyed, Ode to Joy-singing Europhile, still concerned about EU overreach but, nonetheless, a believer that, on balance, our interests were best served by continued EU membership.

I was on the losing side. Having provided a referendum, we had a duty to implement it. Failure to do so would ensure our politics would be scarred by the politics of betrayal.

The only responsible way to do so was with a deal, ensuring that we entered into a deep and special partnership and that we would have a smooth and orderly departure from the EU. But the problem with this is that leaving the EU was always going to be complex. It was never possible to maintain exactly the same benefits of EU membership whilst walking away from the institutions and the rules. Leaving in the abstract was one thing; the specifics of leaving – where detailed trade-offs have to be made – is another.

The Leave campaign made big promises in terms of our independence from EU institutions. It also reassured the public as to the minimal impact on businesses and sectors trading with the EU. The problem is that it is impossible to deliver on both sets of promises at the same time.

Theresa May tried and, in my view, got a good deal – a compromise that struck a pragmatic balance. But, as measured by the absolutist hopes of some Brexiteers, it fell short of delivering the dreamed for ‘independence’. Any deal will. But the cost of failing to reach a deal – in terms of our prosperity, security and the integrity of the UK – is far too high.

Leaving with a deal remains much the best outcome. But, given that Parliament has three times rejected a deal, this is not going to be easy. The Prime Minister clearly wants a deal but he has set out one big red line – the replacement of the Northern Irish backstop.

Will the EU change their position? The purpose of the backstop is to ensure that there is no hard border between Northern Ireland and the Republic of Ireland. This is an important and legitimate objective, and it is unrealistic to think they will abandon the backstop unless there is an alternative that works.

The Prime Minister has accepted that it is for the UK to propose a workable replacement to the backstop. To succeed, it must have the confidence of the people and businesses on both sides of the Irish border. If we engage positively in that endeavour, the EU has always said they would work constructively with us. But if we fail to come up with credible plans, threats of a no deal departure (which will obviously impact the UK more than the EU) will not force the EU to abandon its long-held position.

Assuming a deal is reached (and that is a very big assumption), the deal then needs to get through Parliament. It may well face opposition from a significant number of Conservative MPs who want wider changes to the Withdrawal Agreement. The more my colleagues say they want wider changes, the more remote it appears any kind of deal could be delivered.

Even with the numbers, there is the question of time. The European Council is on 17 October and the Queens Speech debates will conclude on 22 October. Is anyone seriously suggesting that a Withdrawal Agreement Bill can be concluded in nine days? All stages in both the Commons and the Lords in just over a week? Those of us who served in the previous Cabinet will recall that those responsible for managing House business would advise us that the Withdrawal Agreement Bill would take two to three months to complete.

The conclusion is clear. If the Prime Minister is sincere that we leave on 31 October ‘do or die’ (and I believe he is sincere) the overwhelming likelihood is that, unless Parliament intervenes this week, we will leave without a deal. Some may welcome that. But for those of us who believe that this would be a tragic mistake, Parliament will have to step in.