I wish you well.
That is the best way to begin a letter like this, I suppose. The ceremony was tolerable, and you’ve a great deal of friends who could not be more pleased for the two of you.
Mary Morstan is a tolerable woman, and clearly, makes you very happy. So my wedding gift to you is a song. I wasn’t intending to get a gift at all, but Mrs. Hudson was quick to inform me that it was ‘bad manners’.
So I enlisted her help. I have recorded a personal composition of mine for you to listen to at your discretion. It was composed with you in mind, and as you may recall, was played many evenings when you woke from the throws of a nightmare. It’s purpose was to soothe you whenever you were upset or agitated.
I hope you will turn to this song when you find yourself unhappy or uneasy. Mrs. Hudson assisted me with the recording; she was quite an excellent piano player in her day, and was more than happy to accompany me in the piece.
Give my regards and well wishes to your new Mrs. Watson, and believe me to be, my dear friend,
Very sincerely yours,
[actual song is ‘Barcarolle’ by Offenbach, of course, but when listening to it, I always imagined it would be the kind of song Sherlock might compose for John]