Raphael had known Aziraphale since he was but a cherub. He had mentored him and taught him and he knew him. Thus, the Principality's reaction was like a neon light and all the clues suddenly snapped together, beginning with the heavy infernal aura.

He dropped the knife, clattering to the floor. His fingers grew numb and his blood chilled to ice as the realization set in. How could he have missed this?

"Aziraphael..." He moved and placed both hands on his shoulders, eyes fixed on his. "You're in love with a demon."

It was a statement of fact, not a question.