Ultimus haeres (Latin for ultimate heir) is a concept in Scots law where if a person in Scotland who dies without leaving a will (i.e. intestate) and has no blood relative who can be easily traced, the estate is claimed by the Queen's and Lord Treasurer's Remembrancer on behalf of the Crown.
In England, such matters are dealt with under bona vacantia.
References
Ultimus haeres Wikipedia(Text) CC BY-SA