How to handle security with Auto-Versions and Time Machine?

I've upgraded to OS X Lion, which of course now has the new automatic "versions" system.

Today, I created a text file in TextEdit, containing highly sensitive data that I must keep absolutely secure (well, you know -- as best I can.) The file was eventually copied to an encrypted sparse disk image (.dmg) and the original on my desktop deleted trashed and emptied.

But before that happened, Lion had already saved two copies of the file through the new versions sytem --and-- one copy in regular old Time Machine! So much for keeping the file secure. 😐 (OK -- not "copies" but delta data. Whatever. 😝)

EDIT: OK ... I found how to "Delete all backups ..." from within Time Machine. (I feel silly for not finding that before!) But the real question here relates to manual and auto-save versions from the likes of TextEdit and any residual data that may leave lying around, despite the file seemingly having been deleted.

My questions should now be fairly obvious ...

• Does "Delete all backups" from within TimeMachine also delete all data from the "versions" system? One would assume so. But I don't like to assume.
• Can one somehow pre-emptively flag a file to not be recorded by versions or Time Machine?

Someone in some post noted that a file could be "locked" to prevent these issues altogether. But I can find no informtaion about such a thing, either by further googling or poking around in menus locally.

EDIT: Good grief! You spend ages trying to find something, then you post on here and it magically appears. You can click the title bar of TextEdit to produce a pull-down (that's new!), which shows an option to "Lock".

So this one is just about answered by myself -- except for the part about whether "version delta" info is also removed when "Delete all backups" is used from within Time Machine.

Any help will be much appreciated. Thanks.

Bryan.