If there is a need to fill such a position it must first be offered to the person who vacated it.
Not true, as we went through a redundancy process and this is one of the questions I asked, it is because the redundant position is made as the business stands on that day. If things change and you need to employ again, the previous encumbant of the redundant position does not have any rights to that position, although you would like to think it would be offered.
Anyway it detracts from the original post.
We were asked, at CX, to take voluntary unpaid leave, and were told that it could be made compulsory, but as it can not in other places around the world it would be kept at voluntary. If more was needed later it may well become compulsory. I'd rather have a little unpaid leave than people loose their jobs.