69 N. Grant Street, Mid Lake City,
[Subject: Normally bold, summarizes the intention of the letter] -Optional-
Dear Mather Smith,
I regret to inform you that I will have to withdraw the invitation I sent to you for speaking to our student body at Tampa Middle school. We have received a number of calls from concerned parents who do not wish that their children be exposed to any controversial material and so we have cancelled the assembly.
I am highly obliged that you agreed to spend your precious time and also apologize for any sort of inconvenience.