This was the question faced by the Court of Appeal in the divorce case of Hayat Alireza v Hossam Radwan  EWCA Civ1545.
The wife was appealing a High Court Judge's decision that enabled her and her three children to occupy a flat in London owned by the husband's family until the children had grown up or she remarried. The husband was found to have access to wealth of around £16m, albeit all of it inherited. The Judge had reached her decision based on evidence that the wife had a substantial inheritance entitlement on the death of her 'extremely wealthy' father in consequence of 'forced heirship' rules in laws in Saudi Arabia – albeit that not may fall in for a further 16 years or more.
The Court of Appeal decided that although the wife did have a clear prospect of significant wealth in the future and this represented a 'resource' for her, this did not detract from her husband's obligation to provide sufficient funds now to enable her to buy a home for her and the children. Leaving the wife's future in the hands of a series of men 'sat uncomfortably with contemporary mores' and significantly impacted upon her personal autonomy. Although the father had provided financial assistance this did not mean that the court could conclude that he would support his adult daughter in the future as there was no legal duty on him to do so.