How to *force* a UTF-8 coding when visiting a file?

[kj <no.email@please.post>]

Short of adding "-*- coding: utf-8 -*-" to the beginning of a file,
is there a way to *force* Emacs to assume a UTF-8 coding?

I have found that slight corruptions to a file can easily throw
off whatever heuristics Emacs uses to guess a file's encoding.
For such situations it would be useful to be able to tell Emacs
explicitly what coding to use when visiting a file.  IOW, I'm
looking for the "unobtrusive" equivalent to adding "-*- coding:
utf-8 -*-" at the beginning of the file.

thanks in advance!