Yes, if the ex-spouse has not remarried or formed a new civil partnership, and the parties have failed to reach a formal financial settlement order or achieved a clean break, an ex-spouse could make a claim against the Deceased’s estate for reasonable financial provision pursuant to the Inheritance (Provision for Family and Dependants) Act 1975.
Such a claim would have to be brought within 6 months of the Grant of Probate being issued.  A financial settlement will usually contain a clause preventing future claims against the estate of the other party, therefore if such settlement has not been achieved it is likely they can claim.
Read more here.