Note: I don't know if this is how an Earl would address a letter to a servant, even one he considers a friend, but for the purposes of this story, he does.
To John Bates,
My Dear Fellow,
I am writing this letter to let you know that we are working as hard as we can to get the Home Secretary to reprieve your death sentence. Mr. Murray is confident that he will be able to since the circumstances of Vera's death are suspicious.
If, for whatever reason, Mr. Murray is not able to gain the reprieve or overturn, I want you to know that we will take care of Anna. As long as she wants to stay, she'll have a home and a job. Lady Mary has decided that she wants to retain Anna as her Lady's Maid after she marries. If she should decide to leave, I'll make sure that she has an impeccable character reference and will always be available to her if she should need help.
I don't want you to worry about anything, Bates. I don't believe that you are guilty of anything but marrying the wrong woman and being too noble. I will continue to do all I can to prove your innocence.
Your Devoted Servant
Robert Crawley, Earl of Grantham