The fifth Archbishop of Colombo, Most Rev. Dr. John Mary Masson OMI, appointed in 1938, was the last in line of 5 Archbishops of Colombo who were foreign Oblates to dedicate their lives for the sake of the Archdiocese of Colombo.

Archbishop Masson is known for the vow he made to Our Heavenly Mother for the sake of our country to save it from the ravages of the World War II. He also contributed fairly well for the development of the education in the Archdiocese by establishing new schools which exist to this day.

His office as the Archbishop of Colombo ended in 1947, just before the independence of Sri Lanka.