There's a concept that diamond marketers and I have long disagreed upon. As one more tool in their push to convince people they need diamonds to make relationships function, the advertising folks like to use the phrase "for your best friend and your true love." And, to be blunt, that has always seemed to me to be shorting folks one relationship in their lives to deal with the insecurities of another.
If you've truly found such a person and still want to make that claim after the honeymoon phase of a relationship is done, well, congratulations. But there's a test that my best friends have passed that a true love rarely gets the chance to take, and when I look at Sherlock Holmes and John H. Watson of the Doyle Canon, I see them passing with flying colors.
There is an old saying "absence makes the heart grow fonder" that doesn't really apply to best friends in my book. They were great friends to start, and when they go away for a time and return to your life, that same great friendship hasn't changed. It's like they never left. But when your true love leaves, you feel that absence like a hole in your being. You pine. You long. Your heart grows so much fonder that it hurts. And, if and when they return, well, things are not exactly the same as if they never left. (Probably a lot more sex at first, for one thing.)
John Watson of the original sixty stories is always leaving Sherlock Holmes, and every time he returns, they pick up where they left off. Sherlock Holmes even does that "I'm dead. Oh, no, I'm not!" thing and they still pick up right where they left off. To me, that smacks heavily of best friends.
Imagining the angst and drama of a true love that goes through all of the departures and reunions of Doyle's original duo makes their tale something so different that one can hardly focus on the mysteries they're solving. It would be interesting to see a Canon-faithful rewrite of the original sixty that delved into Holmes and Watson as each others' true love, the way Rob Nunn did a rewrite of the Canon with Holmes as a criminal in The Criminal Mastermind of Baker Street, and I know there are folks out there with the talent to do it. It would be a hard emotional journey for said writer, I'm sure, because a Sherlockian's every impulse is to see our two heroes happy . . . and I don't think all their comings and goings (titter if you must) would be a happy love story.
As best friends, though, they seem to do just fine. John can still have Mary for his true love, Sherlock can have crime as his true love, and Canon life goes on.
But, hey, if they were both best friends and true loves, maybe they could get a fancy diamond ring for each other out of the deal.