After the Queen's death, Caspian needed space to mourn, so it was Trumpkin who made the arrangements. He sent the messengers proclaiming her title and name and the nature of her passing to every community in Narnia. He noticed how his old friend's son was taking the news. He checked that some minor rights and privileges of certain Old Narnian groups had been properly recognised and he headed off the inevitable crush of idiots stomping round the place where the queen had died by proclaiming the Crown's support for one (1) official quest to slay the serpent.
Prince Rilian tried to claim the quest.
Sir Rikki bowed with the boneless grace of her people, tail extended for balance. More than one courtier's neck ached in sympathy - her back paws were planted firmly, the fur of her chin was brushing the floor and she was still craning her neck back to look him straight in the eye. She - voice high and chattering - asserted the ancient (and recently revived) privilege that knights of (the recently revived) house Tavi had precedence on all quests relating to snakes.
Rilian was angry and desperate to do something.
Rikki asked innocently if there were any persons who would care to join her on her quest.
Rilian announced - voice cracking - that he was a man knighted and didn't need a nursemaid.
Rikki found him following her four nights later. He was shivering and hungry and she invited him to share her fire and dinner.
Rilian was not in the least grateful.
Rikki amused herself by altering her pose during Rilian's interminable blinks.
The snake and the knight darted around each other faster than Rilian's eyes could follow. He danced around them as best he could, heart in his mouth, and pointed his sword in the general direction of the melee. He didn't know who was winning.
Sir Rikki was winning. Not in the sense that she was in the process of slaying herself a serpent and winning the gratitude of her monarch whilst remaining uninjured. She was winning in the sense that she was more fully self-actualised in this desperate succession of instants than she had been in the rest of her life. This snake was fast and probably evil and almost certainly venomous. This fight was what she was for.