RN Collection: Mary Lou McDonald. Sinn Fein Vice President, Mary Lou Mc Donald, will be elected as the new leader and President of sinn Fein, to succeed Gerry Adams, in February 2018. End. 23/3/2017. Martin McGuinness Funeral. Pictured (LtoR) Sinn Feins new leader in Northern Ireland, Michelle O’Neill ,Sinn Féin President Gerry Adams TD and Deputy Leader Mary Lou McDonald TD at the graveside of Martin McGuinness at the cemetery in Derry City . Photo: Sam Boal/Rollingnews.ie