The Doctor's journal snapped shut and disappeared into his deplthless pocket. He finally gave the trio his full on attention. Jack and Logan still playing the sparring match of testosterone against testosterone; Ianto looking on and hoping the rather ridiculous display would come to a close; and then there was the Doctor, quiet observer.
Perhaps he was trying to make a judgement with regard to Logan and Ianto's mettle. He was already quite aware of Jack's; but the other two? They left a bit for him to question and wonder about. It appeared, however, he wasn't going to be able to get too much information from the task at hand.
Turning away quietly the Doctor was walking away. He had seen enough.