Scotland's Roman Catholic Church faces 'grave crisis', says historian 26 February 2013 Last updated at 08:22 A leading historian says Scotland's Roman Catholic Church is facing its gravest crisis since the Reformation. Prof Tom Devine was speaking after the country's Cardinal Keith O'Brien resigned amid allegations of "inappropriate behaviour." He is contesting the claims by three serving priests and a former priest. Prof Devine said: "This is probably the gravest single public crisis to hit the Catholic Church in Scotland since the Reformation." In his commentary piece published in the Daily Telegraph, he added: "Its effects in the short term are incalculable." However, the senior Edinburgh University research professor believes that, although the faithful in Scotland would be stunned by the "seismic turn of events," the church had a powerful resilience that should not be underestimated. The resignation of Cardinal O'Brien as archbishop of St Andrews and Edinburgh followed claims that he had acted inappropriately to four priests who had been in the ministry in the 1980s. Britain's leading Roman Catholic cleric had been due to take part in the election of Pope Benedict's successor. He had been expected to fly out to Rome and join his fellow cardinals to vote in the conclave. However, Cardinal O'Brien issued a statement on Monday saying he would be resigning with immediate effect and would not participate in the vote. He added: "I have valued the opportunity of serving the people of Scotland and overseas in various ways since becoming a priest.