I have been reluctant to join in this discussion as feelings are understandably running high, and I don't really want to get dragged into a slanging match. However, leaving aside the moral and political arguments, there are considerable practical and legal difficulties with this suggestion, and these can't be overlooked.

If Parliament is sovereign it could presumably pass emergency powers to allow property to be requisitioned. It might also be able to legislate to short-cut the usual CPO process to allow this to happen quickly. However the target here seems to be luxury properties, owned but not occupied by the wealthy. I doubt Corbyn has in mind seizing empty properties where the owner is, for example, in hospital or temporarily working elsewhere. It would be difficult to frame legislation in such a way which would single out rich people's property that would not be discriminatory and contrary to human rights law. It would be wide open to legal challenge, and the people it is aimed at are well able to afford to challenge it. The delays this would cause are alone probably sufficient to make this unworkable.

The other issue is the cost. Requisition is not confiscation, and compensation at market value would have to be paid. According to the Guardian the value of empty property in Kensington and Chelsea is around £644m. Owners might also be entitled to claim for other losses, and have their legal and professional costs paid.   Even if they were only taken temporarily the rental cost would be many thousands of pounds a week. The victims have other urgent needs besides housing, and money has to be found to address these as well. £644m+ could go a very long way.

It would almost certainly be both much cheaper and much quicker for the government or local authority to rent or purchase empty properties of an acceptable standard which are already on the market. To spend more than is necessary to acquire luxury properties to make a political point is not a sensible use of public money, which would be better spent addressing the victims' other needs.