Proprietary estoppel is a very obvious example of where this happens, but I don't think that this is relevant here. Typically this will involve a family farm or business where the parent says "Stay working on the farm and, when I die, all this will be yours" but, that doesn't happen.
To get on to some specific examples that are post Illott v Mitson, there is often an element of ill health or disability or using the money for a specific purpose involved in successful claims.
For example:
In the case of "H Deceased", his entire estate, worth £554k, was left to his spouse who was then in a care home. The son was the executor.
The 50 year old daughter had a complex psychiatric disorder, considerable financial problems and she lived in substandard rented accommodation with two young children. She was awarded £139k
Re H (Deceased) [2020] EWHC 1134 (Fam)
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In the case of Rochford v Rochford in the Peterborough County Court in 2021, the father had mostly disinherited his only daughter. Out of an estate worth £245k he only left £25k to his daughter and everything else to his sister (the daughter's aunt).
The daughter had a severe degenerative disease which prevented her from working. She was awarded a further £85k and also costs against her aunt. The costs are likely as much as the award that was made. These articles from the solicitors that represented the daughter:
https://todayswillsandprobate.co.uk/a-stark-warning-on-costs-in-contentious-probate-matters/
https://www.shoosmiths.com/insights/articles/the-adult-child-strikes-back-rochford-part-36-in-inheritance-act-claims
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Slightly different, as this was a case involving minors, "R Deceased", who were both still at school when their father died but were aged 18 and 17 at the time of the judgment. One had just started university and the other was about to go to university the following year.
The judgment basically said that their costs up until the year after they finished university should be covered. They were awarded £118k and £68k from an estate worth approx £600k after they had been excluded totally.
Re R Deceased [2021] EWHC 936 (Ch)
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Then, more recently, there is the case of Dignam-Thomas v McCourt.
This was rather more complicated. Two daughters made a claim against their father's estate. They both had significant health needs, but they had also been supported financially to some extent by their father before his death. So the claim was made on both bases.
The sisters were awarded £70k and £90k from an estate worth £330k.
Dignam-Thomas & Anor v McCourt & Anor [2023] EWHC 546 (Fam)