nasty hard fail for invalid character (from MS Word html) in a CiviMail

Attempting to save a CiviMail with the following text results in a JS failure. We should fail much more gracefully if we can't cope.

I have attached part of a long email generated in MS Word & copied to CiviMail. I narrowed it down to one line causing the fail. I have attached that line from the original MS Word document (saved as Open Office). If I copy & paste this line to a CiviMail it fails, generating a js error on any save actions - including autosave or attempting to send. It contains a control character.

To replicate create a new CiviMail - paste from the attached file & attempt to send a test message.