In the United Kingdom, the title of Knight is bestowed upon certain people. Should you find the need to correspond with a Knight in the United Kingdom -- or anywhere else -- you need to address him correctly. The opening and closing of your correspondence must be correct as well as the form of address you use on the envelope you mail your correspondence in. Fortunately, addressing a Knight is not a difficult task.
Begin your correspondence by addressing it to the Knight using the proper form of address, which is "Sir" or "Dear Sir insert Knight name here."
Close your letter by signing your name underneath the phrase "Yours faithfully."
Address the envelope to a Knight by using his title, name and letter of the relevant Order. Address your letter in the following format:
Sir First and Last Name of Knight GCB
Letters of the relevant Order differ depending on the Knight with whom you are corresponding.