evidence: The Democratic Unionist Party (DUP) will elect its new leader on Friday after Arlene Foster announced her intention to step down. [...] Sir Jeffrey Donaldson is the DUP's Westminster leader and is currently the longest-serving MP from Northern Ireland. Born in Kilkeel, the 58-year-old has said his decision to enter politics was influenced by the IRA murder of his cousin and RUC officer Samuel Donaldson in 1970.