Fr Justin at in his post Nova and Vetera - Vespers: a little more posted the above photo to draw attention to the crucifer and his tonsure.
The gentleman is Brother Alban of the Canons Regular of the New Jerusalem, based in St Louis, Missouri. They are regular visitors to traditional events in Europe and I have met them a few times now, as well as being able to listen to a lecture given by their founder Dom Daniel Oppenheimer. Brother Alban assisted me in the group I was teaching at the Merton Conference in the summer, arranged by the Latin Mass Society to offer training to priests wishing to learn how to celebrate the Classical Roman Rite.
Seeing Brother Alban holding that crucifix brought back memories of about 25 years ago when, as a student in Rome, I assisted in the same capacity at Mass celebrated by Pope John Paul II. It is a very special thing in itself to assist as a server at a Papal Mass but you also get to meet the Holy Father personally:
Do remember the Canons Regular of the New Jerusalem in your prayers. They are very generous in remembering others