I’ve been having so many thoughts about this post by @ineffableplan that eventually I decided not to hijack it and write my own essay instead.
The thing is, we love to joke about Aziraphale and Crowley being bad at communication, but I think that, at least when it comes to communication with each other, 99% of time they’re insanely good at it.
Because they know each other so well. Every single thing they do and say carries more meaning than it seems at first. It’s like they speak their own language, that only they understand. And in a way, that’s exactly what it is. Aziraphale knows that if he keeps repeating that it has to be Crowley who removes the stain, Crowley will do it. (And I think it works both ways - I think Crowley knows he will be asked, too.) Crowley knows that if he presents an issue from a different angle, Aziraphale will agree to participate/help. (And again, Aziraphale knows that Crowley will present an issue from a different angle if he says no at first.) They speak each other’s language more fluently than anyone on Earth, in Heaven or in Hell.
And that’s why even in the show, which provided us with the extra 30-minute-long footage of pure repression and pining, they absolutely do have an established relationship. They know. Their story has never been a “two people obviously care about each other but are scared to confess because they’re not sure the other one feels the same way“ story. Guys. They have confessed. Multiple times.
“Out of the question. It would destroy you.“
“We can run away together - Alpha Centauri.“
“I can’t have you risking your life.“
“You can stay at my place, if you like.“
(Not to mention the entire body swap scene which is just one huge confession itself.)
And additionally, they both acknowledge that Something is going on (no matter how we as viewers decide to define this Something). Crowley acknowledges it by being offended when Aziraphale calls it fraternising. Aziraphale acknowledges it when he says, “You go too fast for me, Crowley,“ and “There is no our side, Crowley, not anymore“.
Because, as I’ve already said, their story is not about establishing a relationship, it’s about breaking free from the fear of punishment for being in that relationship. Why would Aziraphale hide that he even knows Crowley personally if nothing was established? Why would Crowley need insurance if there was nothing going on? Multiple plot points literally stop making sense if we don’t treat their relationship as something that already exists and affects their lives and jobs, and most importantly, themselves.
That’s why everything they do is never easy to read for other people (save for the wall slam which Sister Mary saw as an intimate moment, and the “I’m going home, angel” scene). That’s why the most important things stay between them, where no-one else can hear - in the Bentley, in St. James’s Park when nobody is listening, on the bandstand in an empty park, on a bus stop. That’s why Aziraphale says, “We don’t know each other,“ loudly, and “Hell won’t just be angry, they’ll destroy you,“ quietly. Because every interaction is a risk, to some extent. Because there’s a lot to lose.