John Smith stayed fairly close to the door, wincing a little as she called him on his little fib. "Oh, I did knick it," he looked to the sign. "Whole thing, knicked it out of a museum. With my granddaughter, Susan." You didn't know that, did you Rose? Moving closer to a shelf he set the sign down - not because it was particularly heavy, but because he felt he didn't really need to hide behind it.
"So..." he pursed his lips a little, putting all those important thoughts in order. There was a fantastic bruise that ran up under his jaw and it took a lot of effort to remember that he couldn't very comfortably scratch at his cheek at the moment. "I'm sorry," he said quietly, taking that step forward and giving Rose Tyler a sincere look. He wasn't hoping for anything in particular - and he certainly wasn't holding out for outward forgiveness. No, he was fully prepared for Rose to take her time and beat him up a little.
"Did they send you someplace interesting yesterday?" Apology over, time to talk about something else.