If you ever get the opportunity of buying some of the old CTS pamphlets which Fr Thurston wrote to explain the rites of Holy Week, grab it.
Here, for a taster, is a passage from his Palm Sunday Pamphlet.
"[W]e have retained a vestige of the solemn entry into the city or cathedral in the halt still made by the sacred ministers in front of the closed church door. Of old, as the procession came back to the town - that is in their symbolistic conception of the scene, as our Saviour drew nigh to the walls of Jerusalem - high up among the battlements over the city gate, or over the cathedral porch, a group of choristers would be looking out ready to greet His approach. The procession comes to a standstill, and there above their heads the fresh young voices of the choir-boys ring out through the still morning air, chanting the words:
Gloria, laus et honor tibi sit, Rex, Christe Redemptor,
Cui puerile decus prompsit Hosanna pium. "