Nobody uses any form of address in the room. Even though we speak English (where such address is not necessarily inappropriate) both T and I are too mired in the local usage, where it would not be appropriate. Or at least that's how it is for me - I could never address somebody in speech unless I had to get their attention or identify them, it would feel unnatural to me. In writing, I use the shortened form of T's first name, he uses my first name. No titles or last names. Again, I would not use a title or last name with anybody in Sweden, it's just not done except in a very few contexs that are irrelevant for me, and that usage carries over to my English even though I know very well that the rules for address are different in English.