IHTM12192 | Succession: Simultaneous deaths (commorientes): General law (England and Wales)
From HM Revenue & Customs · Inheritance Tax Manual
If two or more people die in circumstances in which the order of their deaths is uncertain, for example in a road accident, the devolution of their estates is governed by the Law of Property Act 1925/S184. This provides
that the deaths are presumed to have occurred in order of age so that the younger is presumed to have survived the elder,
but
this is subject to any court order, and
where the deaths are of husband and wife or civil partners (IHTM11032) and the elder died intestate, the intestacy rules apply as if the younger spouse or civil partner had not survived the elder.