The DUP has revealed how the Prime Minister is trying to woo Peter Robinson's party to back him in the event of a hung Parliament after the next election.
David Cameron hosted a drinks reception for DUP MPs at No.10 on the night that Gerry Adams was arrested.
The timing of the reception – where non-alcoholic drinks were available for any DUP teetotallers – was said to be coincidental, though the Government was told about Mr Adams' imminent arrest two days earlier.
East Antrim MP Sammy Wilson was not present for the soiree but said his party was being "courted, tested and probed" on their attitude if there was no clear winner after the General Election – or even earlier if there was a split between the sometimes tenuous Conservative and Liberal Democrat coalition.
"That is the way life works," said Mr Wilson, who was at a constituency meeting while the reception was being held.
He describe how his party was being sounded out and buttered up at Westminster.
"When you speak in the House of Commons you get spokesmen from the various parties coming and saying, 'That was a good speech, glad you said that'," he said.
"In the normal course of events you would never really get a comment like that. It is part of an attempt to strike up a friendly accord with ourselves because we may be important in the future. People don't want to make enemies of us and that increases our influence."
The DUP is the fourth largest party in Westminster and its eight MPs could be invaluable in a hung Parliament.
The reception, news of which first broke in The Guardian, took place on April 30. The reception was in the garden of 10 Downing Street.
A DUP spokesman confirmed that the Prime Minister "kindly provided some hospitality for our MPs".
The developing courtship has irritated Sinn Fein, which has never had a one-to-one with Mr Cameron, and fears the Government will make concessions to the DUP.
While the Prime Minister was content to talk about it, he downplayed the significance. "It is only right the Prime Minister talks to other groups and parties in Parliament," Mr Cameron told the BBC.
"I was having a meeting with leading DUPs to discuss trying to win from the Libyans some compensation for the fact that Libyan Semtex, given to them (the IRA) by Colonel Gaddafi, is still being used in Northern Ireland. The drinks we had were an offshoot from that meeting."
Nigel Dodds, the leader of the DUP's eight MPs, said of the reception: "I wouldn't overplay it or underplay it. It is not a big deal. What we are very pleased about is the fact that the Prime Minister appointed the national security adviser, Sir Kim Darroch, to negotiate with Libya on this issue. I have been in Libya myself to pursue this case and this is a good response from the Government."
Sinn Fein has five MPs, who don't take their seats. As a result they don't figure in the Parliamentary arithmetic.
This week Martin McGuinness accused the Tories of "cosying up" to the DUP ahead of the Westminster election in case they needed a deal in its aftermath.
Mr McGuinness complained that Mr Cameron now had frequent meetings with the DUP, but had never met Sinn Fein as a political party.
Labour and the Conservatives are almost neck and neck in the polls after a surge in Tory support, according to polling earlier this week. Polling one year out from the next General Election puts the Opposition on 34%, with the Tories up five points on last month to 33%. The Liberal Democrats were on 8%, down two points.