If your father married whilst having an existing Will in place the effect of this is that his Will is automatically revoked. Therefore he will be deemed to have died intestate and the rules above are applicable to the administration of his estate.
However if his Will was written after he got married and he did not make provision for his new wife then she will be entitled to claim under the Inheritance (Provision for Family and Dependents)Act 1975. Her claims would be based in the fact that she had not been adequately provided for under the terms of his Will.
If you are worried that this is the case then please come along and discuss this with our Wills and Estate Planning department.