Thanks, thats what I thought, I'm in the process of reviewing the security on a sql instance which I've inherited, but currently one login has sysadmin rights and has been getting used to take adhoc backups of a database without using the COPY_ONLY command therefore its knocking out the backup chain for diff backups etc.

I don't want to remove the sysadmin right straight away before I can determine who or what is using this login.