Sherlock Holmes: When I met you for the first time yesterday, I said "Afghanistan or Iraq?"
Dr John Watson: Yes. How did you know?
Sherlock Holmes: I didn't know, I saw. Your haircut, the way you hold yourself, says military. The conversation as you entered the room - said trained at Bart's, so army doctor. Obvious. Your face is tanned, but no tan above the wrists - you've been abroad but not sunbathing. The limp's really bad when you walk, but you don't ask for a chair when you stand, like you've forgotten about it, so it's at least partly psychosomatic. That suggests the original circumstances of the injury were probably traumatic - wounded in action, then. Wounded in action, suntan - Afghanistan or Iraq.
Dr John Watson: You said I had a therapist.
Sherlock Holmes: You've got a psychosomatic limp. Of course you've got a therapist. Then there's your brother. Your phone - it's expensive, email enabled, MP3 player. But you're looking for a flat-share, you wouldn't waste money on this. It's a gift, then. Scratches - not one, many over time. It's been in the same pocket as keys and coins. The man sitting next to me wouldn't treat his one luxury item like this, so it's had a previous owner. The next bit's easy, you know it already.
[indicates back of the phone, which has been engraved with the inscription "Harry Watson - from Clara XXX"]
Dr John Watson: The engraving?
Sherlock Holmes: Harry Watson - clearly a family member who's given you his old phone. Not your father - this is a young man's gadget. Could be a cousin, but you're a war hero who can't find a place to live. Unlikely you've got an extended family, certainly not one you're close to, so brother it is. Now, Clara - who's Clara? Three kisses says romantic attachment. Expensive phone says wife, not girlfriend. Must've given it to him recently - this model's only six months old. Marriage in trouble, then - six months on, and already he's giving it away? If she'd left him, he would've kept it. People do, sentiment. But no, he wanted rid of it - he left her. He gave the phone to you, that says he wants you to stay in touch.
Dr John Watson: How can you possibly know about the drinking?
[cuts to a close-up of the phone's charger port, showing obvious scratches around it]
Sherlock Holmes: Shot in the dark. Good one, though. Power connection - tiny little scuff marks around the edge. Every night he goes to plug it in and charge but his hands are shaky. You never see those marks on a sober man's phone, never see a drunk's without them. There you go, you see? You were right.