Hat-tip to the Hermeneutic of Continuity. It is from an article by the Cambridge academic John Casey; the whole of which is worth a read.
Nearly twenty five years ago, a Pole was dining in my college in Cambridge. He told us that he had been an altar boy in Poland, and had often served the masses of the Archbishop of Cracow. A year or two after that prelate, Karol Woytila, had been installed in the See of Rome, he decided to visit him, for John Paul II never became too grand for his old Polish friends. The Pope (so he told the story) strode up to him, punched him lightly in the chest, and began: Introibo ad altare dei ... to which our guest responded: Ad deum qui laetificat iuventutum meum. ("I will go unto the altar of God'' - "To God who giveth joy to my youth.'') This was the opening exchange between priest and server of the old "Tridentine'' Latin mass, abolished in the early 1970s, and the two continued it right down to the Confiteor. Then the Pope shrugged his shoulders and said: 'Well, that''s no use to us anymore.' His old altar boy replied: 'No, Holy Father, and that''s why I no longer go to church.' To which the Pope (he said) instantly rejoined: 'Don''t blame me. Blame that maniac John XXIII!'