Ahead of the event, the Irish Times recorded nationalist concerns about the arrangement:
Peripherally, there are mutterings of concern that to cement the deal Cameron, should he become prime minister, would tinker with the British-Irish agreements that led to peace and political progress in Northern Ireland; that he might disavow the Downing Street Declaration commitment that Britain has no "selfish, strategic or economic interest in Northern Ireland". Such a move would certainly cause problems, especially with Dublin, Sinn Féin and the SDLP. "We support the current agreement and want to make it work," says Paterson. He is absolutely "emphatic" on this point, he adds.
Nevertheless, the tone of Cameron's speech was a long way from that of the Downing Street Declaration:
Standing up for the Union isn't just about expressing our important feelings about our shared heritage.
It's also a rational argument based on mutual interest.
Together, we are the fifth largest economy in the world.
Together, we have a seat at the top table and are listened to in a way that other countries can only dream of.
Together, we have one of only five permanent seats of the United Nations Security Council.
Together we are a major player in the EU, in NATO and other international organisations.
And together, we have the British military - one of the most respected armed forces in the world.
Northern Ireland punches above its weight in Britain's armed forces and Britain punches above its weight in the world because of the expertise and bravery of those forces.
Indeed, nothing embodies the Union better than our military bonds.
More coverage over at Slugger which is liveblogging the event.
Get our weekly email