LONDON—British Business Secretary Kwasi Kwarteng said on Thursday the European Union had been inflexible over renegotiating the Northern Ireland part of the Brexit divorce accord and cautioned Brussels that it was not a deal that would last for ever. “A deal is a deal but it wasn’t something that was going to last forever,” Kwarteng told Sky. “It was something that was flexible and we want to make it work more smoothly.” “Article 16 … it is something that we could do, to suspend it, we’ve chosen not to do that, that’s not our opening position and we want to be able to negotiate and have a conversation with the EU about how best to go forward.” Britain demanded on Wednesday that the EU agree to rewrite the Northern Ireland protocol which covers post-Brexit trade involving the province just a year after it was agreed. The EU immediately rejected that …