It is “not realistic” to expect stability in Northern Ireland under the terms of the Brexit deal, the next leader of the Democratic Unionist Party (DUP) has warned. Sir Jeffrey Donaldson said he would speak to Boris Johnson to underline his message. His comments came as Brexit minister Lord Frost said it was “hard to see” how the Northern Ireland Protocol, the part of the Brexit deal at the heart of the controversy, can survive in its current form. Donaldson was the only candidate to succeed Edwin Poots after his short-lived leadership of the DUP collapsed. “I will be speaking with the Prime Minister at the earliest opportunity to emphasise that it is not realistic to expect stability when every unionist representative in the devolved institutions opposes the Northern Ireland Protocol,” he said. “The Government and those who claim to be protectors of peace and stability must step up and …