In an impressive ceremony, you personally confer knighthood upon Harold Godwinson, making him a knight of the duchy and taking him onto your council of ducal advisors. You have decided to make Harold your friend.
Rivalon of Dol has betrothed his daughter to count Conan of Brittany. This is only agreeable to you, because Rivalon is playing both sides of the field at once, and agrees to invite Conan to his castle of Dol to discuss terms of the marriage: meanwhile, you will approach with an army and surprise Dol, and thus Conan, trapping him there. Then with him in your power you can dictate terms to your benefit. That is the plan, but you only put it out publically that an expedition is going to enter Brittany to aid count Hoel in regaining his lands.
Harold comes along, at your invitation. He impresses you with the rescue of two of your knights, who foolishly endangered their own lives by charging into the river Couesnon as your army entered Brittany: by this act of selfless bravado, you know Harold as an exceptionally strong and courageous man, but also one who lets his heart rule his mind: you tuck this piece of information about his emotional character into the back of your mind for possible future use.
The campaign is rather inconclusive, to say the least. Someone leaked word of your plans to Conan, and he manages to slither out of Dol just in time to escape your trap.
He leads you a merry chase, clear to Dinan, where he holds out long enough to endanger your army: your lines of supply are weak and long, your army beginning to feel the pinch of hunger: for Conan's people have stripped off most of their provisions ahead of your army's advance and hidden it. To save face, you accept a two-year truce with Conan and withdraw back into Norman territory.
After feasting and impressing Harold with your generosity as a lord, you:
Send him home with gifts, requesting that he aid you in becoming king of England.
Hold an oath-taking ceremony, wherein Harold becomes your vassal, and promises to aid you in becoming king of England.