The ambitious Chamberlain, Pierres de Cruzat, related to the Foix family, sought revenge for the King's decision not to choose the candidate presented by the Foix family to marry Doña Blanca, the new heir to the throne.
Pierres steals the chalice with the aim of returning it before Sunday with a slight modification, consisting of a forged signature of the silversmith Jacques de Montpellier and the motto: ‘France always first in my heart (Carlos III)’
This would prove that the famous Chalice, a symbol of the monarch's loyalty and love for Navarre, was in fact the work of French and not Navarrese craftsmen (a rumour that was already circulating in the city).
The Chamberlain was the hooded man who bribed the Gatekeeper Tomás to close the southern Gateway and thus force the carriage to go along another road, outside the walls, where it would be easier to attack it (and this also sets things up to make the accusations against the Baker seem more well-founded). The Chamberlain is a hardened military man, and he had no trouble knocking out the driver and the guard.
To build an alibi, Pierres involves his fiancée, Doña María de Nas, Chambermaid to the Infanta. He also gives Doña María the note written in invisible ink to be given to a silversmith called Jean-Paul. María locks herself in a forbidden chapel in the palace, to ensure that no-one will see her during this time.
It’s almost certain that the Chamberlain planned to pretend that when he picked the Chalice up at mass, it slipped from his hands, causing one of the large enamels on the stem to fall off, revealing the secret signature and motto.
Many people in Navarre would take great offence at this, seeing it as an intolerable mockery that would fuel suspicions towards the King (who is of French origin) and his intentions.
The seeds of mistrust and dissatisfaction would be sown in times that already remain very unstable.
And you know what they say, ‘troubled waters make for good fishing’.