The High Court ruling allows the Duke to hand the Blenheim estate to trustees who will have 'full power and responsiblity for the management and the conservation of the palace'. The effect is to ensure the Marquess never gains control of the estate when he succeeds his father.
The new trust arrangements will allow the Duke to live in the Palace until his death, after which the Marquess would then have the right to live in the private apartments.
Currently the Duke has all the powers of management of the Parliamentary estates. But he has repeatedly voiced his concern about the estate passing to his eldest son and has indicated he would like it to pass initially to his younger son, Edward.
In March, the trustees of the estate explained the reason for the action. Their statement said: 'Over the last 10 years the trustees and the Duke have become increasingly concerned as to the fitness of Lord Blandford to exercise the powers of management as tenant for life of the estates when he succeeds his father to the Dukedom.
'The well-publicised problems of Lord Blandford during 1993 convinced the trustees that it was necessary to take steps to protect the Palace by removing from Lord Blandford the powers of management on his succession to the Dukedom. The Duke reluctantly agreed this was necessary.'
It also stressed that the aim of the legal action was not to disinherit Lord Blandford, but rather the 'protection' of the estate and its future beneficiaries.
The estates were conferred by Acts of Parliament in 1704 and 1706 on John Churchill, the first Duke of Marlborough, as part of his reward from a grateful nation for his victory over the French at Blenheim, in Bohemia. Blenheim Palace and its estates, valued at more than pounds 100m, are now a flourishing business with a total turnover estimated at pounds 10m a year.
Before the hearing, the Duke of Marlborough described his love of his family home and why he took the legal action. He said: 'I've lived for Blenheim really, I love the place. I'm very proud of the place.'
Talking about his son, Jamie, he said: 'I think that there is always a black sheep in all families. I do not think there is anything new about that . . . he has had every chance, hasn't he?'