As one of the king's top guards, Martin was always on time to ensure Rhesus's safety. Although he knew this particular youth possessed only mediocre skills, the king had specifically chosen him for the purpose of serving as his eyes and ears. Half of his problem would be solved by bringing a guard near him whom no one could doubt.
Martin would not be able to attract the attention of the enemy. Because of this, they would instead choose to ignore him. That's what made him a special guard who would inform the king of every daily activity of the soldiers standing nearby. Even the enemies inside the palace wouldn't be on their guard in front of such a mediocre soldier.