Before a noble son may hold land and title he must prove himself as a Knight Errant, roaming the kingdom in search of deeds worth a fief. Errants arrive at every muster uninvited and unpaid, sleeping in hedgerows, polishing hand-me-down armor, and pestering the heralds for a place in the front rank.
In battle they are magnificent and barely governable. They charge early, charge deep, and charge things wiser knights politely avoid, for a young man with everything to prove weighs death against obscurity and finds obscurity heavier. Bretonnian generals treat them like a drawn bow — you do not steer a Knight Errant, you choose the moment to let go.