Quote 10
At sight of Mr. Utterson, he sprang up from his chair and welcomed him with both hands. The geniality, as was the way of the man, was somewhat theatrical to the eye; but it reposed on genuine feeling. For these two were old friends, old mates both at school and college, both thorough respecters of themselves and of each other, and what does not always follow, men who thoroughly enjoyed each other's company. (2.4)
Dr. Lanyon and Mr. Utterson have a strong friendship.
Quote 11
He gave his friend a few seconds to recover his composure, and then approached the question he had come to put. (2.10)
Mr. Utterson is considerate, but never abandons his objectives.
Quote 12
Or else he would see a room in a rich house, where his friend lay asleep, dreaming and smiling at his dreams; and then the door of that room would be opened, the curtains of the bed plucked apart, the sleeper recalled, and lo! there would stand by his side a figure to whom power was given, and even at that dead hour, he must rise and do its bidding. (2.13)
Rather than believe that Dr. Jekyll is in fact friends with Mr. Hyde, Mr. Utterson’s first conclusion is that Mr. Hyde has some sort of control over Dr. Jekyll. This interpretation is most likely colored by their friendship.