Originally Posted by
MileHighLawyer
Use of the title Rt Hon is limited to members of Her Majesty's Privy Council.
I'm afraid this is simply not true.
Consult any source you like on the subject, e.g. Debrett's, Whitaker's Almanack, Burke's. You will see it is correctly applied to peers as I described, including those (most) who are not members of the Privy Council.