In Northern Ireland the British government must always be seen to act in good faith. I learned this personally when trying to bring together bitter old enemies, the Democratic Unionist Party leader Ian Paisley and Sinn Féin's Martin McGuinness, who at the time had never exchanged a word, let alone negotiated with each other.
Some months before they so improbably became the “chuckle brothers” ruling Northern Ireland’s newly devolved government, Paisley wanted an absolute assurance that Sinn Féin would back something historically impossible for it: policing and the rule of law. He assured me he would govern with Sinn Féin but only if that was guaranteed: it was his bottom line.
McGuinness, with the president of Sinn Féin Gerry Adams, in turn had the superhuman leadership challenge of persuading their rank and file, including former IRA combatants, to do so. They would only attempt this task if Paisley would do what he had always renounced: sharing power with former "terrorists", or " the devil " in his immortal rhetoric. How could they be sure he would?
After exploring the detail with both, I told them Paisley would and I told Paisley Sinn Féin would. Both had learned to rely on me and Tony Blair because we understood and empathised with both sides.
We didn’t have to agree with either, but we had to respect each standpoint. We were neutral, non-partisan, with no vested interested in any of Northern Ireland’s parties.
Damaging
That’s fundamentally why Theresa May’s proposed deal with the DUP is so damaging for the Belfast Agreement and the peace process.
Managing Northern Ireland's peace process is like carrying a tray of champagne glasses over a high wire. It needs forensic care and constant attention. That, from No 10 downward, was never demonstrated by David Cameron or May – more concerned about party than progress in Northern Ireland, spurning the British parliament's bipartisan stance which was so important to the hard-won process of winning the peace.
Cameron in 2015 had at least one cosy dinner at No 10 with DUP MPs – some of whom gleefully reported to me that parliamentary arithmetic, not Stormont's functioning, was on the menu.
With a DUP deal as her only way of staying in power, how could May say no to the unionists, for example, in the vital but tortuous negotiations to resurrect the devolved government and assembly, disturbingly suspended now for months?
May's refusal earlier this year to resolve this latest Stormont crisis by convening a summit with the taoiseach – a move that, under Blair and Gordon Brown, frequently resolved seemingly irretrievable breakdowns – was inexplicable.
Legacy issues
What’s more, the DUP could also press its own agenda on conflict-related legacy issues, such as blocking the prosecutions of soldiers and police accused of serious crimes. There is a strong argument for a time limit on investigations into crimes during the era of terror and sectarian violence. However, this has to be applied across the divide or not at all, otherwise agreement with republicans and nationalists will be immeasurably more difficult than it already is.
Alongside this, a Tory-DUP deal could cause its own internal difficulties. May’s preferred hard Brexit means the Border between the North and the Republic would be the external EU customs frontier, requiring both goods and people movement to be checked and cleared, with a tariff levied. That both contravenes the Belfast Agreement and jeopardises the increasing integration of both economies.
Despite supporting Brexit, the DUP wants – and to maintain domestic political credibility must have – a soft Border. And that means the UK being at least within the European Customs Union, if not the Single Market.
Declaring Northern Ireland a “special zone” to try to solve this problem, as the European commission appears to have suggested, is not acceptable to the DUP because it would imply a distinct status within the UK in breach of its unionist imperative.
Working-class base
Besides, DUP members are not Tories. They have a significant working-class base. They don’t buy Tory austerity. They will insist on much more public investment and spending. Nor will they accept policies to reduce state pension benefits or May’s reactionary “dementia tax”.
They are seasoned, tough negotiators – none more so than Nigel Dodds, their able parliamentary leader. And they have a pathological opposition to imposed deadlines, as I also know from personal experience. A Tory-DUP deal, therefore, will be both painful for May and painful for political stability and peace in the North.
Peter Hain was Labour MP for Neath from 1991 to 2015, and Northern secretary from 2005 to 2007.
– Guardian Service