Mr Robinson referred the OTR letters as an example of the "price unionism and Northern Ireland as a whole would pay if we were simply to allow Stormont to collapse".The First Minister threatened to resign from his post over the revelation that almost 200 fugitive IRA suspects were sent letters from the government telling them they could return to Northern Ireland without prosecution.It led to a political crisis and fears the Stormont institutions could collapse - however those concerns receded after Prime Minister David Cameron announced a judge-led inquiry into the letters."It was bad enough to see the concessions that were given as part of the Belfast agreement, but this invisible scheme, to use the words of Gerry Adams, went far beyond that," Mr Robinson told those attending the event in Newcastle."I am hopeful that the work of the inquiries that have been set up will get to the truth but let's be clear, I will not rest and this party will not rest until we do get the truth."Mr Robinson added: "Whatever the criticisms and complaints about the status quo - from those who want to tear Stormont down, end devolution and return Northern Ireland to Direct Rule from Westminster with Dublin input - it would be political and economic madness to take such a route."He added that it was an "absolute outrage that some unionists argue that the best solution to all of this is to hand back the levers of power to those who behaved in this way"."They may now attempt to disguise their true intentions by railing against Stormont, but they know - even if they studiously avoid telling you - that if they were to succeed in wrecking the present process, the only alternative is to hand power over to London leaving Dublin once more calling the shots."This is not conjecture it's the bitter lesson of history and the legacy we lived through and faced down when we became the leaders of unionism. Unionists were side-lined and without power. Dublin acted on behalf of nationalists and London was, at best, neutral."