As a discretionary exception to the general rule of learning spells, the GM may deem that for a particular campaign, each starting character may already know a few spells. The idea is that the spells were learned during the character's back story.
This should be facilitated using the regular grimoire
These spells will be relatively low powered and must be chosen in order taking into account regular spell prerequisites. The GM will define a maximum XP amount to spend retroactively, according to usual spell learning rules. This XP amount may or may not be contingent upon the character's Magery attribute.