When you are married you are entitled to look at all assets and liabilities that are available, and consider those against the section 25 factors of the Matrimonial Causes Act 1973 when you divorce. That includes things like your age, the children that may be dependent, the length of your marriage, your respective contributions and so on. It does not take into consideration how devoted you may have been to your spouse or whether or not you have been unfaithful. If Ms Gray was awarded £90 million in her divorce settlement, it was because that was what the Court deemed fair in all the circumstances. 

The fact that her 'boyfriend' is now trying to have a share of £20 million of assets that accumulated during their relationship is neither here nor there in terms of how she initially had the money. It may have been her money. 

If Mr Hurley wants £20 million worth of assets he can't rely on the fact that he's been in a relationship for 6 years and that he is essentially a 'common law husband' because there is no such thing! Either he paid for those things, it's in their joint names, or something has happened for him to rely on a promise that Ms Gray made that he would have a share. Even so, it's a civil action not a family law one which will follow the usual civil law costs rules. It is an expensive exercise and one which he will hopefully have been properly advised on. 

The moral to the story....think things through and have an open conversation about how you hold your assets in any relationship. Get advice on co-habitation agreements or pre-nuptial agreements.