Sam McBride: Long ago, the DUP prepared for this extraordinary moment

Arlene Foster and the DUP have a 'red line' over the use of passports to travel within the UK
Arlene Foster and the DUP have a 'red line' over the use of passports to travel within the UK

If you want to know what the DUP will look for in exchange for sustaining Theresa May as prime minister, don’t read its manifesto.

Instead, the clues as to what that party will now seek from the Tories are to be found in a document which the party put together two years ago ahead of the last general election.

Unlike its manifesto for this election, which was written on the explicit understanding that there would be a thumping Tory majority, that document was drawn up for precisely this scenario.

In 2015, the expected hung Parliament never materialised and the document was forgotten. No longer.

‘The Northern Ireland Plan’, a 12-page route map for this situation, sets out 45 DUP priorities for Westminster, many of which are financial, including an increased budget for Stormont to allow for greater real terms health and education spending, capital investment in schools and hospitals, better terms to allow Stormont to slash corporation tax and infrastructure investment in a range of areas.

But the list was not purely financial, incorporating “proper border controls and a tougher immigration policy”; removing allowances from parties who refuse to attend the House of Commons (ie Sinn Fein), legislation to reform the structure of Stormont and new parading legislation to remake the body which rules on Orange Order parades.

One of the non-financial priorities which the party highlighted is particularly relevant after recent events – the redefinition of a ‘victim’. Under Northern Ireland law, terrorists shot by the police while attempting to murder are regarded as victims, on a par with those they have killed, something which has long enraged unionists – and plenty of non-unionists as well.

Instructive as the 2015 document is – and a senior DUP source yesterday confirmed its relevance to the current situation – two things have changed since then.

At that point the DUP was openly hoping to bargain between Labour and the Tories, selling its votes to the highest bidder.

Since then, the party has moved much closer to the Tories and, due to both ideological differences with Jeremy Corbyn and distrust of his links to Irish republicanism, the DUP has made clear that it will never put him into Downing Street.

Therefore, having restricted any deal to the Tories, the price which it can extract may not be as lucrative.

The second major change since 2015 is Brexit. The DUP is an enthusiastically Eurosceptic party with most of its MPs sharing the views of the right of the Tory Party on the issue.

But the party has one red line on Brexit – and perhaps the only one of its entire negotiation: no post-Brexit internal UK borders.

The DUP, like every other Northern Irish party, wants to keep the current free-flowing border with the Republic of Ireland. But the peril in that stance is that – in order to secure the UK’s borders and to regulate the flow of goods – passport and customs control would be implemented at ports between Northern Ireland and Great Britain.

Last year I asked Arlene Foster about that prospect of citizens having to use a passport to travel within their own country and she ruled it out categorically as “a red line for us”.

At the launch of the party’s manifesto a fortnight ago, Nigel Dodds, the DUP’s Westminster leader, repeated that assurance, saying: “We’re not leaving the European Union to get rid of some of its shackles to impose more restrictions between the constituent parts of the United Kingdom – we’re certainly not doing that.”

At Prime Minister’s Questions last November, Mr Dodds asked Mrs May if she could guarantee that Brexit “will not result in any change, alteration or impeding of the way regions, countries and people within the UK connect with one another”. The prime minister responded: “I’m very happy to give the Right Honourable Gentleman that assurance in relation to movement around the United Kingdom. There is no change that is going to take place.”

Marrying that assurance with the DUP’s desire not to see the Irish border at the Irish border will not be easy.

But suddenly – and just four weeks after the DUP leader all but conceded that it would have no role in choosing the prime minister – it has the power to put its demands at the top of Westminster’s agenda.