In 1982, he was assigned as Bishop of Berlin and All Germany. In April 1986 he was appointed Ruling Bishop of the Diocese of Great Britain and Ireland and Rector of St. Alexander Nevsky Church in Copenhagen. In 1990, he was elevated to the rank of Archbishop. In 1997, he was also appointed Overseer of the Russian Ecclesiastical Mission in Jerusalem. Archbishop Mark has been one of the most ardent supporters of Church unity between ROCOR and the Moscow Patriarchate, and worked tirelessly to see this goal achieved. From 1993 to 1997, he headed the dialog between the German-based dioceses of the Russian Orthodox Church Outside of Russia and the Moscow Patriarchate in the reunited Germany. Since 2000, he has been the President of the Committee on the Unity of the Russian Church, and since 2003, the President of the Commission on talks with the Moscow Patriarchate. This was a large part of the impetus which brought about the reunification of the ROCOR and Moscow Patriarchal churches, which finally took place in 2006.  7–12 June 2009 he was a participant of the Pan-Orthodox Pre-Council Conference IV of the Russian Orthodox Church. Since July 27, 2009 he is Member of the Inter-Council Presence of the Russian Orthodox Church.  8 December 2016 the Synod ща ROCOR heard the report by Archbishop Mark and then accepted his resignation from the Diocese of Great Britain  On December 10th, 2019, the feast day of the Kursk-Root Icon of the Mother of God, Archbishop Mark was made a Metropolitan by the Holy Synod of ROCOR in recognition of his 40 years of Episcopal service to the Church. Although largely symbolic, this is the first instance of multiple active Metropolitan Bishops in ROCOR, apart from those who were previously made Metropolitans prior to the inception of ROCOR and retired Metropolitans.