Interview: Irish backstop "vital" for Northern Ireland, says mayor of British border city Derry

Mayor of Derry John Boyle works in his office in Derry, a Northern Ireland border city in the United Kingdom, on March 20, 2019. The "backstop," a mechanism to avoid a hard border on the island of Ireland after Brexit, is "vital" for Northern Ireland, said John Boyle, mayor of British city Derry which sits on the border. (Xinhua/Han Yan)?