Sherlock,

Honestly, I hope you never have to read this. If you are, it means Mary and I are dead. Sorry about that.

Mary's bullying me into writing this now, while our daughter's still young. It was only last week we asked you to be her godfather.

To be honest, Sherlock, I have no idea what I should write. I don't want to imagine my little girl growing up without her parents, the thought of me missing her first steps, first words, first day of school, first relationship is … not worth thinking about.

But if you are reading this then I must be gone (I mean I better be - if you steal this letter and read it while Mary and I are still alive rest assured I will kill you). But there are some things I want you to know.

First, I have always trusted you. More than any man I've ever met. I remember the vow you made at my wedding, and I know you'd do anything to keep it. You've proven that already. I know you'll keep my daughter safe. I know you'll protect her as I would.

But Sherlock, protecting her isn't enough. I need you to love her. I know you do - the look on your face when you first saw her in the hospital is proof of that, so don't bother denying it. But I need you to show it. She has to know she is loved, and that her mum and dad loved her more than life itself, more than anything.

Don't make her feel stupid. I know what comes easily to you baffles the rest of us, but I don't want her thinking you resent her for not being smart or that she's not good enough; you're extraordinary Sherlock. You always have been. Not everyone can be a genius, but I want you to treat her like one anyway, even if she's bottom in her class. I don't care how clever she is. I don't care if she hates crime stories. (No pictures of decomposing bodies until she's at least 18.)

I want her to be safe, and happy. I know you'd probably die before letting any harm come to her. Make her smile too, Sherlock. Make her laugh. I don't care what she's interested in, but even if it's a stupid TV show about ponies, I don't want you telling her it's wrong to love it or that it's stupid, even if it really is. Make sure she never misses an episode. If she wants to learn ballet or boxing or whatever, make sure she has everything she needs to be as brilliant at it as she can. Help her.

And if she ever has a boyfriend, don't kill him. Give him a chance. (Unless he seems dodgy, then call Lestrade.)

You're probably still wondering why we chose you to be her guardian. I know you're still confused about it, even if you said you understood.

I told you once that you were the best and wisest man I had ever known. Nothing's changed. You're my best friend. And if my daughter can't have me as a father, knowing she'll have you … Well. There's no one I'd rather have raise her.

I know this will be hard for you. We've only had her a month and we're already shattered! But seriously Sherlock, I know you can do this, I know you'll be a great godfather. I believe in you. Always have, always will.

You're my best man, Sherlock Holmes. You've saved my life more times and in more ways than I can count. I owe you more than I could ever possibly repay, so instead of trying, I'm going to ask one last favour of you. Take care of my daughter. Love her, hug her, laugh with her, protect her, hold her when she cries, and dance with her for me on her wedding day.

Thank God - you just texted me. Something about a beehive. I'll wrap this up and head over to Baker St.

There's a lot I want to say to you, and to her, but I've never been a man of many words. So I'll just say this: I love you both, and I always will. Nothing could ever change that.

Right. That's the gist of it. Time to get to Baker St. I'll see you soon, Sherlock.

To the very best of times, eh? John

PS. I'm sorry I died, Sherlock. I hope you're ok. Take care of yourself. For me.

AN: A sequel to this, The Watson Wing, has been posted, showing Sherlock's reaction to reading John's letter. Please click on my profile to find it!