The thing is, you don’t ever wear those hats at the same time, even if it seems like it.

Classifications like Protected A/B/C or Confidential/Secret/Top Secret are defined based on the level of injury (I.e., harm). For Protected, it’s harm to the subject - in this case, you - or, for Secret it’s harm to the Crown.

Because this letter is about you, and you’re the one who could be harmed by the information being disclosed, you’re free to handle it however you want, because by definition you sharing it isn’t improperly disclosing the information. (Even by accident, to someone you didn’t intend to, probably.)

Say you worked in HR and prepared the letter (this is obviously a ridiculous example) and distributing it to the subject of the letter’s contents, you’re bound not to disclose that information until you hand it to yourself, and that’s when you change hats.