Horses of knights were trained to be conscious of what their master's feet and knees meant. Hard squeezes vs soft, only using one side over the other, and even the way their knights leaned into the saddle was enough to send a message to these horses. They were trained this way because, in battle, a knight's arms were often in use carrying a shield or wielding a sword—although a lance was always more efficient at such a distance that horses offered.
Since horses and knights had such deep-rooted bonds, it seemed like an impossibility that Sammy would be there without Irene unless something unbelievably awful happened. Scenarios pushed their way into Arthur's thoughts, and he felt sick to his stomach.
