The mother (and daughter) of all family quarrels

It began as an ordinary family row over love, power and money and has become the mother – and daughter – of all quarrels. The affaire Bettencourt has intrigued and occasionally shaken France for three years, and now it threatens to destabilise L'Oréal, the world's largest cosmetics company.

After losing a long legal battle with her only daughter, the L'Oréal heiress, Liliane Bettencourt, 88, France's wealthiest woman, has been declared senile by a French court. Her €18bn (£15.8bn) fortune has been placed under the control of her estranged daughter and two grandsons.

The affair has tangled, and often poisonous, roots in modern French history. It draws some of its bitterness from the post-war and inter-war anti-Semitism of the French haute bourgeoisie.

L'Oréal was founded in 1909 by Liliane's father, Eugene Schueller. Liliane, his only child, was involved in the company from a young age. In 1950, she married right-wing journalist and politician, André Bettencourt. Their daughter Françoise was born three years later.

Liliane has always been an enthusiastic socialite. Françoise became a shy, quiet girl, and brilliant pianist. In 1984 she married – against her parents' initial wishes – Jean-Pierre Meyers from a wealthy, French Jewish banking family. Five years later, it emerged that both Eugene Schueller and André Bettencourt had worked for the virulently anti-Semitic Cagoule movement before the Second World War.

Some insiders suggest that the rift between Françoise and her mother began at that time. That may be too simple. Ill-feeling between the L'Oréal matriarch and her Jewish son-in-law does seem to be part of the explanation of the family quarrel. However, Françoise remained very close to her father until his death. She appears never to have been very close to her mother.

Soon after her father's death in 2007, Françoise began to complain about her mother's close friendship with a playboy writer and photographer, François-Marie Banier. The relationship was never sexual. Mr Banier is gay.

Françoise Bettencourt-Meyers said that Mr Banier had turned her mother against her. She also objected to the extravagant presents which her octogenarian mother had showered on the left-wing, professedly money-hating photographer. Her gifts were estimated to be worth over €1bn, including art-works, cash, life insurance policies and an island in the Indian Ocean.

In late 2007 Françoise began the first of a series of legal actions to try to prove that her mother was senile and was being cheated by her entourage. Mr Banier was not the only culprit, according to Ms Bettencourt-Meyers. She also protested about the activities of Patrice de Maistre, the manager of Liliane's personal fortune and a pillar of French society. Late last year, the original mother-daughter quarrel appeared to have been resolved.

Mr Banier agreed to give back most of his extravagant gifts. Liliane agreed to speak to Françoise. The Elysée Palace is reported to have brought pressure on the Bettencourt family to agree to this reconciliation. But within weeks, mother and daughter were quarrelling again. Françoise made a new attempt to prove that her mother was not responsible for her actions and was being badly advised by her entourage.

On Monday a court near Paris accepted medical evidence that Liliane Bettencourt was suffering from "dementia, a moderately severe form of Alzheimer's disease and a slow, degenerative brain condition". She was placed under the control of her daughter and two grandsons. Her lawyers have appealed against the ruling.

The saga continues...