Before Vespers, the canons and clergy in attendance gather on the west side of the main altar, facing the tomb of the Prince of the Apostles; the Litany of the Saints is sung, with the invocation "Sancte Petre, ora pro nobis" repeated three times.
This is the signal for the procession to begin slowly making its way down and back up the longest church nave in the world.
When the procession returns to the apse, Vespers is sung as usual on Sundays on holy days of obligation, underneath the magnificent Chair of St. Peter by Bernini. The celebrant (very often a bishop) is accompanied by two coped assistants, one of whom reads the lesson after the psalmody.
The other coped assistant, (not a thurifer in cassock and surplice) performs the incensation of the choir and the faithful; I have been told that this custom is a holdover from the pre-Conciliar traditions of the Basilica.
The choir then processes to the front of the altar, to the singing of the hymn Vexilla Regis, while two canons of the Basilica ascend to the balcony of the pillar of St. Veronica. (Each of the four pillars that support Michelangelo's massive dome was built also with a staircase inside it, and a balcony from which one of the principal relics of the church could be exposed on solemn occasions such as this one.) An antiphon and versicle are sung by the choir, followed by the prayer of the Veil of St. Veronica. A set of silver bells are then rung, and then the Veil is shown to the faithful from the balcony. This is not the place to comment on the authenticity of the Veil, which has a long and very complex history. I can only say that I have witnessed this ritual several times, and on each occasion, when it is shown to the crowds, the church becomes completely silent, even though many of the people present are obviously tourists who have no idea what is happening. (The canon here on the right is Mons. Camille Perl, former Secretary of the Ecclesia Dei commission; due to a technical fault wholly beyond my kenning, I had to convert this photograph to black and white.)
Here one can see the exposition of the Veil in the year 2008; my thanks to Mr. Lucas Viar for permission to use this video.
Deus, qui nobis signatis lumine vultus tui imaginem tuam relinquere voluisti: per passionem et crucem tuam tribue nobis, quaesumus; ut sicut nunc in terris per speculum et in aenigmate ipsam veneramur, ita facie ad faciem venientem judicem te securi videamus. Qui vivis.The original version composed by Pope Innocent III in 1208:
God, who didst wish to leave Thy image to us, who are marked with the light of Thy countenance: through Thy passion and Cross grant us, we beseech Thee; that as now upon the earth we venerate it through a glass darkly, so in safety may we see Thee face to face when Thou comest to judge. Who livest etc.
Deus, qui nobis signatis lumine vultus tui memoriale tuum ad instantiam Veronicae sudario impressam imaginem relinquere voluisti, per passionem et crucem tuam tribue nobis quaesumus, ut ita nunc in terris per speculum et in aenigmate ipsam adorare et venerari valeamus, ut facie ad faciem venientem iudicem te securi videamus.Qui vivis.
God, who didst wish to leave as a memorial of Thee to us, who are marked with the light of Thy countenance, an image impressed upon a cloth at the urging of Veronica: through Thy passion and Cross grant us, we beseech Thee; that we may now upon the earth be so able to venerate and adore it through a glass darkly, that in safety may we see Thee face to face when Thou comest to judge. Who livest etc.
[Re-publication with the permission of the auctor]