Dear John,
If you are reading this, I'm dead. Actually dead. It means I didn't survive Moriarty, and I am now beyond judgement, and the press, and everything else you ever feared.
But you were the one who never judged me, you never lost faith in me, you were the only one. There are people I've known better, and people I've known longer, but there is nobody I know who I've been so close to, or I think has been so close to me.
This letter isn't just to say goodbye. Everything I would say in a letter like that you would already know. This letter is for something more. There's something I've always meant to tell you, something others have only ever guessed at.
I love you. I have always loved you, from the very moment we met. You are the most amazing person, in my opinion, in the world. People say I'm clever, but I don't have the knowledge of people, or of the world that you do. You save people's lives. You saved my life.
You are a brilliant writer, too, something I have never told you, and I have never told you how much I appreciate your glowing representation of me. You are essential in my life, and I could not survive for one week without you. I hope the same is not true of me, and that you can live your life in happiness without me.
Please, if you ever cared for me at all, live your life without me. There are friends out there, waiting to meet you, who will become just as important in your life as me and, probably, more. And if you did ever love me, there is someone out there who would make you far happier than I ever could.
Goodbye, John.
Sherlock.