Mark Harper is a former Chief Whip, and MP for the Forest of Dean.

We now have two candidates left in the Conservative Party leadership contest, and I am sorry to disappoint – but I will not be disclosing which I am going to back, although whoever wins will have my full support to make their leadership of the Party I love as successful as it can be. I think the next Prime Minister, whoever it is, needs a realistic plan to keep our promises and deliver Brexit.

Like most Conservatives, I’d love to leave the EU as soon as possible, and I voted to leave on March 29th and April 12th. The current extension to Article 50 runs to October 31st – which is the EU’s date, not ours. As a former Chief Whip, it’s my judgement that it isn’t credible to say either that the present deal can be renegotiated, or that a new one can, and be got through both Houses of Parliament by the end of October.

But I don’t think we should carry on kicking the can down the road, either. After our disastrous showing in both the local and European Parliament elections, I want to make sure that Britain has left the European Union before we have any more elections. We must leave between October 31st this year and March next year. We can’t go into the 2020 elections for important Mayoral positions and Police and Crime Commissioners in England and Wales without having delivered our promise to leave the European Union.

If the Government is faced with the choice of leaving without a deal or never leaving at all, I believe we should leave without a deal. My view is that the Commons will allow this to happen if Conservative colleagues are persuaded that the Government has done everything it can to secure a deal, but it simply isn’t possible to do so. I don’t believe that colleagues will be persuaded of that by October 31st, so leaving without a deal on that date isn’t credible.

From the moment the new Prime Minister assumes office, he should take every step required to ensure that we are in a position to leave without a deal if that proves necessary.

So how are we going to get a new deal? The key is to build strong relationships, both across the Conservative Parliamentary Party, with our DUP allies, and with our European partners.

First, the new Prime Minister needs to properly engage and listen to the views of our Conservative MPs. The Conservative Parliamentary Party, having been heard and properly consulted, can then unite around the new strategy.

We can only get Brexit delivered, as I argued last October, with the votes of Conservatives, our DUP allies and a handful of backbench Labour MPs. We cannot trust the Labour front bench: its job is to oppose us, and Jeremy Corbyn wants to destroy us.

We must also face up to the reality that the current unamended ‘deal’ is dead. The only thing for which Parliament has signalled approval is the present ‘deal’ without the backstop.

So must go back to Brussels and open real and transparent discussions to change the backstop. After the Brady amendment’s approval in January and credible work on alternatives, I haven’t seen any evidence that the Prime Minister or Cabinet seriously pursued this course of action when it had the chance to earlier this year.

The second element of a credible Brexit plan must involve setting the right relationship with our EU partners – both the Commission and the heads of government of the member states.

The new Prime Minister and Cabinet must use their diplomatic and communication skills – both bilaterally and collectively – to get the tone of these relationships right. We need to show the EU what a positive post-Brexit relationship could look like – covering trade and the economy, security and defence – and clearly articulate how it’s best for both sides to get this right.

Then we can put forward a proper plan to change the backstop and protect the constitutional integrity of the United Kingdom.

The third part of this Brexit plan should involve building strong relationships both with the Republic of Ireland, and with both communities and all Parties in Northern Ireland.

This final element of the plan is crucial. The EU will only move on the backstop with reassurance about both the integrity of the Belfast Agreement and the Single Market. We need a serious and credible figure to lead the Northern Ireland Office and tackle these issues head on.

It is vital to rebuild a proper relationship with the Republic of Ireland. We work very closely with Irish officials on everything from the operation of the Common Travel Area, to our efforts to crack down on smuggling at the present currency, VAT and excise border and regularly share intelligence and security resources to ensure both countries are kept safe. This was something I saw first-hand when serving as Immigration Minister under David Cameron.

Our relationship with the Republic of Ireland should not only be with the Taoiseach and Tánaiste, but also with the main opposition party, Fianna Fáil. As a general election in Ireland becomes a less distant prospect, we need to avoid the backstop becoming a partisan electoral issue in that contest.

In Northern Ireland, we need to make swift progress in re-establishing the Executive at Stormont, driven by a renewed effort from the new Prime Minister and Secretary of State. As the Conservative and Unionist Party, we owe it to everyone in Northern Ireland to restore a functioning devolved government.

This task will be difficult, but the role of Northern Ireland in achieving a successful exit from the European Union for the whole United Kingdom together will be critical.