[5] During the siege of Guimarães by Alfonso VII, then the county's political headquarters, the Emperor reportedly demanded an oath of vassalage from his cousin Afonso Henriques; Egas Moniz addressed the emperor, informing him that his cousin accepted submission.

However, after relocating his capital to Coimbra (1131), Afonso Henriques felt an urgent need to destroy the ties that bound him to Alfonso VII.

As Afonso Henriques did not live up to what was agreed by his tutor, Egas Moniz, having learned what happened, went to Toledo, the imperial capital, accompanied by his wife and children, all barefoot, dressed in white and with a tether around the neck.

Introducing himself to the Emperor, he let him dispose of his life and of his own as a pledge for maintaining the oath of allegiance promised by him but not fulfilled by his pupil.

This part of Egas Moniz's life is retold by Camões in the Lusíadas Song III (stanzas 35-40).