The deal between the Conservatives and the Democratic Unionist Party to maintain the new government at Westminster has focused attention on a party little known outside Northern Ireland. The DUP’s social conservatism – particularly its opposition to abortion and gay marriage – has led to protests, and its image is still largely defined by its founder, the late Ian Paisley. But today’s DUP is not quite the rabble-rousing party of the 1970s, although its culture is still formed by Northern Ireland’s distinctive Protestant fundamentalism.