Empty to Trash - This Item will be deleted immediately - fixed

I tutor was slightly annoyed because when he deleted a file on a Hard Drive it would come up with the question:

Are you sure you want to delete "blaa blaa"?
This item will be deleted immediately. You can't undo this action.

Yet on an identical Hard Drive in the same computer it simply deleted (moved) it to the trash.

I quickly had a look at it, and checked the difference between the drives and found no difference.

I did a quick search on the internet for this dialogue box and found this which looked interesting (lots of stuff about the trash)

In the end I worked out it was because the .Trashes file on the HD probably had the wrong permissions, which was probably set for the first user which used it. I simply deleted it:

rm -R /Volumes/Scratch\ Disk/.Trashes

Done!

Of course this would be set for the new user. One option would be to tick the "Ignore permissions on this volume".