Head of department,
Dear Mr Jonathan,
This letter has been drafted to make you aware of the fact that I am resigning from the post of the sub editor. The news might come as a shock; but consider the context in which the resignation is being made to you. The last annual meet of the organization saw the announcement of me being promoted to the post of the editor from the post of the sub editor.
The promotion letter has reached to me and hence this letter considering the application for the resignation from the post of the sub editor has been put into effect. I wish that the resignation application from the post of the sub editor, put forward by me, is accepted at the earliest so that I am able to acquire the new post and shoulder the responsibilities which the organization has entrusted to me. I hope for a quick and favourable response.