Sherlock had drifted off into his own mind. Despite his quite acute hearing, he had been so preoccupied that it was a bit of a shock to feel John's knees against his. Instinctively, he tensed up and looked towards whatever it was that had disturbed him.

The shocked and angry look faded immediately, replaced by a soft smile.

"Oh. Hello, John." He said softly, almost slightly shyly.