Believe it or not, Arthur actually had to debate with himself about whether or not he should come to Eames with this information. Now that he has finally admitted to himself that he kind of cares about Eames' well-being he has to check himself whenever he wants to share anything remotely political just in case it's too much information to share across factions. This is something he has deemed vague enough to share and important enough to do it right away, which is why he goes straight from Hillingdon House to Eames' front door after he's done working there for the day.

It's early evening when he rings the bell, looking up and down the street as he always does and has done multiple times on his trip here just to check for a tail. It's a combination of paranoia and habit that he doesn't care to break, and with this it might be more pertinent than not to make sure no one's around to overhear.