The first angel Sherlock ever come close to was an older man holding a police badge, at the time he had hair that was just silvering along the sides, a kind, but tired look in eyes that crinkled slightly at the edges and dusty, blue-grey wings.
Sherlock was using his charm and looks on a young girl he'd deduced as a runaway, she was probably barely legal and he was offering her a straw and her choice of long white lines along glass table tops, it was an elaborate trap that if it had worked, would have compounded the guilt and fear, until she felt too desperate to get back in contact with the people she knew before eventually tearing her away from her family completely.
With a few kind words and gentle hands, the angel had managed to usher the girl out of his carefully set trap and eventually back home to a worried mother without resorting to the standard kill the demon from a long distance tactic most angels used when they sensed him.
Both angry and surprised, Sherlock confronted the angel and demanded an explanation and a name.
The angel pierced him with kinder eyes than any other angel he'd met before.
"Lestrade, killing anything for no reason, even a demon like yourself is a waste, for all your elaborate designs, sometimes all it take is a few kind words and a shoulder to lean on to turn people from a dark path."
Sherlock stared as the angel ... Lestrade ... walked away, still making no attempt to execute him or force him back into hell.
Rather stupidly, as there was a strong chance Lestrade would suddenly change his mind and remove him, Sherlock asked him why.
"You seem interesting."