It was a very complex case and this is why it went to court. No one could say who died last or who died first.
Under normal rules if the children died last then Colin would have inherited their share under a valid will. But, because the will became invalid due to the circumstances, it went to court.
Naturally the heirs would be Pam and the next of kin to Neville which would be AP and KP....If memory serves me right AP had to contest and was awarded his share in court for himself and his sister.
The soul living heir would have been Jeremy, but he would not have gained everything under the terms and conditions of the will...
It was and still is complicated.
Regarding adoption. When you have been adopted legally the birth parents have no rights. The adopted children are equally entitled to inherit from the adopted parents as much as their boilogical children. If there is not proof of a legal adoption then that is different. 
The law at the time was if you can't establish who died last you presume the oldest died first. That is what Basil Cock did.
But there was evidence to suggest June died before Nevill so by rights Nevill's relatives should have got everything. If they didn't settle a court woudl have had to decide whether the evidence was sufficient to say Nevill died last or inconclusive in which case June is presumed to die last. Rather than Pam risking eveyrthing would go to Nevill's relatives she decided to settle and Nevill's relatives decided to settle rather than risk the court deciding Pam should get it all. The settlement resulted in Nevill's relatives getting his and June's hers.
The current law scrapped the presuption of the youngest dying last and requires a beneficiary to outlive the testator by 28 days or each is treated as predeceasing the other which results in the same thing as the settlement achieved.
