One of the myths which some have attempted to propagate around Brexit is that the Democratic Unionist Party's support for leaving the European Union was based on a desire to see a so-called 'hard border' between Northern Ireland and our neighbours in the Republic.

That is simply untrue. I can say that as a campaign director for the DUP during the EU referendum, but also because of everything we have said and done since that time.

When Arlene Foster addressed the Killarney Economic Conference just over 18 months ago, she made clear that the principles guiding the DUP's stance on Brexit were a desire to see the referendum result respected, but cognisant of the unique set of circumstances that we in Northern Ireland and the Irish Republic have.

Some of those unique circumstances were first set out in a joint letter penned alongside the then deputy First Minister Martin McGuinness in August 2016, just a matter of weeks after the referendum.

That letter was possibly the first public demonstration of the DUP's desire to see agreement reached for a managed and orderly exit from the European Union.

The authors were on differing sides of the referendum campaign but could focus on shared concerns and a shared desire to see those overcome.

Those two pages were a representation of the political progress made in Northern Ireland and still hold out the prospect that a consensus can be developed to deliver that orderly and managed exit from the EU.

The collapse of the Northern Ireland Executive has not just meant that decisions are left untaken in relation to schools, hospitals and the other vital public services everyone in Northern Ireland relies on.

It has cut off the structures where the spirit of that letter between Arlene Foster and Martin McGuinness could be built upon. It has removed the Executive where agreement could be sought within Northern Ireland, but also the North South Ministerial Council which could have provided a platform for issues of mutual concern across the Border to be addressed. Just think where we might be now if those institutions had been functioning over the past two years.

Nowhere are the divisions on Brexit more sharply expressed than in relation to the backstop. There is an obvious temptation within the European Union to seek reassurance on the backstop amongst those who already support it.

However, if there is a lesson to be taken from Northern Ireland on this issue, it is that progress will be most quickly made through difficult discussions between those who disagree rather than between those who already share the same opinion.

The backstop is presented as a protection for the peace process, but it exists without unionist support. Recently a number of parties in Northern Ireland sent a joint letter to Donald Tusk in support of the backstop. It was devoid of any unionist signatory.

The lesson of the peace process is that progress can only be made when both unionists and nationalists can give support to an agreement. There is a significant irony in the backstop being held up as protection for the Belfast Agreement when it stands outside both the letter and spirit of that agreement.

The principle of consent and parity of esteem should be seen by all as central to that agreement. Yet despite unionism being virtually unanimous in its rejection of the backstop, this is not considered to be outside those core principles.

To be clear, I do not want to see a return to the 'borders of the past' between Northern Ireland and the Republic. There are good economic reasons to avoid such a return, but I also recognise the symbolism it would have for a large number of people in Northern Ireland.

The avoidance of such a border, however, cannot come at the price of erecting a new barrier between Northern Ireland and the rest of the United Kingdom in some kind of Northern Ireland-only backstop.

Three quarters of all Northern Ireland's goods are sold and traded with the rest of the United Kingdom so such a border would come at a much higher economic cost than North-South trade barriers.

It would be more than just symbolic for anyone who cherishes Northern Ireland's place as part of the United Kingdom and would represent a clear change to the relationship between Northern Ireland and the rest of the United Kingdom, thus breaching the principle of consent.

That is why we need to agree alternative arrangements to protect cross border trade and cooperation in the form of practical solutions that do not breach the core principles of the Belfast/Good Friday Agreement.

One of the key factors in reaching any agreement is the relationships built between the participants on either side. There is probably no one who recognised that and exemplified it better than former Taoiseach Bertie Ahern.

He did not share the viewpoint of unionists during discussions, but was able to recognise and understand them. As one of the main architects of the Good Friday Agreement, his recent comments that a Brexit solution must be supported by unionists may not just be borne of that ability to understand unionist concerns, but of the hard political reality that anything not commanding cross-community support is doomed to failure.

It is right that hard-won peace in Northern Ireland is taken seriously, but we should be conscious that those who would drag Northern Ireland back to the violence of the past have been attempting to do so over many years.

Nothing should be said which could allow them any excuse or cover for those murderous desires. Projections that the peace process is fragile or that violence may return can become self-fulfilling prophecies as they allow those who have always been wedded to violence and terror to claim space in which to operate.

If a week truly is a long time in politics, then the time between now and October 31 means that the opportunity to find a solution still remains. The DUP is committed to achieving that deal and the same desire exists within the UK Government.

We can draw upon the lessons of the peace process in Northern Ireland in that quest for agreement.

What we know is that the shared desire to reach an agreement can help ensure that insurmountable hurdles are overcome. We can reach an agreement that is acceptable not just to the European Union but to the UK Parliament; an agreement that is acceptable to unionists as well as nationalists in Northern Ireland.

There is still time available for a solution to be found, if there truly is the will for that to happen. We remain resolute in my desire to see such an agreement reached.

In seeking to ensure we build upon the progress made in Northern Ireland, then it must surely be right to use the lessons learned in Northern Ireland to guide attempts to secure a deal before October 31 and to protect the hard-earned progress made in developing relationships north-south and east-west.

Sir Jeffrey Donaldson MP is chief whip of the Democratic Unionist Party

Sunday Independent