As Eddie says, it's the whole of the deceased person's estate which is relevant.
If they were survived by a spouse or civil partner everything goes to the spouse unless the value of the estate exceeds a quarter of a million pounds. (Then, if there are children of the deceased person, they also get a share).
If there's no surviving spouse or civil partner the children get everything.
https://www.kingstonsmith.co.uk/wp-content/uploads/2016/06/Intestacy-Rules-flowchart-if-you-live-in-england-1.pdf
Note that with large estates (of over £325,000, or £650,000 if the deceased person had earlier received the whole of the estate of a spouse or civil partner who died before him/her) there's Inheritance Tax to be paid. In practice that might mean that some of the shares would need to be sold.