As a mountain walker, one of the most frustrating mistakes one can make in bad weather is taking the wrong route down. As the pleasant prospect of a dry and warm destination grows in one’s mind, so does the dawning realisation that the route is not leading there, usually setting up a difficult conversation with one’s companions as to whether to press on in the hope of correcting the mistake or retracing steps to where one started, and who is to blame.

The last time this happened to me was in a winter whiteout in Scotland — it was only the disappearance of our route into the near vertical chaos of a rock-filled gully which finally clinched the decision. The subsequent cursing as we struggled back up hundreds of feet of icy mountainside was, however, a price worth paying for ending the day alive.

These experiences spring to mind as I contemplate the state Brexit has reached. For more than two-and-a-half years we have been following a route, led by the Prime Minister, which is intended to take us out of the EU without undermining our economy or security while honouring the referendum result. But with less than 50 days to go the signs that we have lost our way are all about us. So is the mounting evidence of present and future damage.

My household insurer has relocated its corporate base to Luxembourg and Barclays has shifted £155 billion of assets to Dublin in anticipation, as it will enjoy no future certainty of operation in the EU from here. The manufacturing industry, which should be able to trade freely under the ideas in the “political declaration” negotiated by the Prime Minister, is looking askance at the future. Nissan’s decision on investment in Sunderland is just one of numerous examples of external investors marking time. Last year inward investment to our country was only about a quarter of what we were getting in 2016.

The Prime Minister insists that all will be well if her deal is accepted and uncertainty removed. The problem is that it does no such thing. She has done her best, but the result is deeply unsatisfactory. We are leaving into a void, bound by every EU rule for the years of “transition”, with no idea of our future trading relationship.

It has become obvious that the Cabinet is deeply divided on what that relationship should be. But whatever form it takes — ranging from the “managed no-deal” of the so-called “Malthouse Compromise” to a Norway- style relationship with a customs union and high levels of regulatory alignment — none will be superior to what we have at present in terms of economic stability. What, one has to ask, are we going to get in return for these second- rate futures? The much-vaunted trade agreements with third countries are withering into insignificance before our eyes. We are heading towards not even being able to replicate the ones the EU already enjoys.

That then leaves the ability to “take back control” of immigration, an assertion rather undermined by the reality that as immigration from the EU, which we can’t currently control, is going down, that from outside, which we can, is rising to fill the jobs gap. As for escaping the jurisdiction of the European Court of Justice — a must for every Brexiteer — the harsh truth is that any continuing relationship will leave it with influence over our lives while we lose the ability to influence EU law.

Yet faced with these facts Brexiteers demand that we press on to a no-deal departure now. They do this against the overwhelming evidence of the deep and lasting damage it will do and the likely break up of the United Kingdom that will follow. I have received a stream of angry emails insisting that this is the “people’s will” and that there is no alternative. They threaten civil unrest — always to be carried out by others — if they don’t get their way.

Just as I hope I shall always do on mountainsides, these calls to rising levels of irrationality have to be resisted. The public are not fools. The evidence is that they know well and by a growing margin that Brexit is an ill-fated venture and they want a say on the outcome. They are against no-deal because they know it is a risk-laden fantasy. My duty as an MP is crystal clear in trying to make sure they get both another say on Brexit and that no deal is prevented.

The next weeks are likely to be decisive in this respect. The opportunity exists for the House of Commons to rise to this crisis and show the common sense that could get us out of difficulty. But that means putting aside the shallow considerations of party political advantage and having the courage to be honest with others as to what is happening. Insisting that all will somehow be well if Brexit goes through now, rather than insisting on a pause and a measured reconsideration, is an abdication of our responsibility.

We were all elected to try to improve the lives of our constituents. We may curse at the burden resulting from our mistakes as we retrace our steps, but we have a duty to get our country through this in one piece.

Dominic Grieve QC is Conservative MP for Beaconsfield and former attorney general.