When Gordon Brown was Prime Minister from 2007–2010, I was privileged to be his Northern Ireland adviser. On the whole it was a relatively quiet and stable period. (Tony Blair and his adviser Jonathan Powell had considerably tougher problems in Northern Ireland to deal with than Gordon Brown or his team.) Of course we had crises galore during our time at no.10. But we only had one crisis over Northern Ireland.

In early 2010, the deadline for devolution of justice & policing powers to Belfast was due, but being held up by a bundle of disputes between the Unionist DUP & the Republican Sinn Fein. We were unable to settle these differences through normal means. So in early February we had three sleepless days & nights holed up in Hillsborough Castle in Northern Ireland, with the Northern Irish parties & the Irish Taoiseach, trying to hammer out a deal.

Each party had their own rooms in Hillsborough. Diplomacy was shuttled between them, via what felt like an interminable cycle of meetings in multiple combinations. These discussions were like playing chess on multiple chessboards all at once, with constant impasses, shouting, walk-outs & deal-making. It was an emotionally fraught time, especially as we were running on the traditional Gordon Brown diet of coffee, bananas and Kit-Kats, not getting daylight or sleep.

After 72 hours we eventually got a deal, involving multiple compromises, careful drafting, a few calculated silences, and of course the promise of extra cash. The DUP and Sinn Fein leaders are some of the best negotiators you will ever come across. And for good reason. Their combination of cunning and passionate commitment support an uneasy and messy kind of politics, but it is a politics that ensures Northern Ireland keeps going forward, rather than retreats into the dangerous division of a previous era.

Here’s the point: the deal would have been impossible if we in the UK Government had been thought to have interests beyond that of being an honest broker. Plain and simple. Impossible.

Now we face new, multiple crises in Northern Irish politics: an executive that has already been suspended for six months, a new generation of leadership on both sides that has not established strong working relationships; and the spectre of a looming Brexit raising real fears of the return of a ‘hard border’ between north and south, will all the worrying consequences that might bring in its wake.

When crises hit Northern Ireland, the primary responsibility for sorting them out lies with the parties in Belfast. But Dublin and London are indispensable supporting players too. The UK Government’s periodic role as an honest broker between the Northern Irish parties is now needed again. It has a duty – to the heroic, courageous moves towards peace on all parties in the recent past, and to the people of Northern Ireland now and in the future – to be & to appear impartial.

And this is why the Conservative-DUP deal is so concerning. Any UK Government formally reliant on any Northern Irish party simply cannot be seen as the honest broker it needs to be. And without the integrity that comes from the appearance of impartiality, the UK Government will be a force for instability rather than stability at a time of serious difficulty in Northern Ireland.

The Government really should abandon the idea of a formal deal. They are playing with fire. And the stakes are too high to risk it.