[River may not have admitted to traveling, but mentioning the Doctor's name is all she needs to do for Ianto to make at least some connection. You don't know the Doctor without being involved in time travel at at least some level yourself. Even if it's only peripherally.]

Well. The one and only. If ever there were a time traveler to get to know, I suppose that would be the one.

[He tries to keep his voice and his expression as neutral as he can as he continues:] He does make his way around, doesn't he...