Override site policy to delete specific messages
We're using Enterprise Vault 8 on Windows 2008 Server to archive mailboxes from Exchange 2007. The company policy is that users are not allowed to delete items from the vault, which is enforced at site level due to the "users can delete items from their archives" setting being cleared. We have a retention policy to retain archived items forever.
However, we have some emails in a particular mailbox which have been archived and shouldn't have been, so I now need to delete some specific messages from a particular vault. How can I override the site settings for a particular mailbox, or for an administrator account to allow me to delete these messages?