This unprecedented attempt to disinherit a legitimate heir is by no means a simple matter for his father, the 11th Duke of Marlborough.
However much His Grace might prefer his second son, Edward, 19, a relative paragon of achievement who is now at Cambridge, to inherit the title, he is compelled by the 1704 Act of Parliament that created it, and by primogeniture, to allow Jamie to become the 12th Duke of Marlborough on his death. The title could only be diverted by a further Act.
What the duke hopes he can do is put the family seat, Blenheim Palace, with its 11,500 acres and assorted farms and villages in Oxfordshire, into a different form of family trust, which his wayward son cannot touch. The combined value of the estate is estimated at between pounds 50 and pounds 100m.
James Morton, editor of the New Law Journal, said the basic procedure of varying the terms of a trust was not uncommon in the Chancery Division, the part of the High Court which deals with inheritance.
Many families have trust funds for tax purposes; often an estate will be passed directly from a grandfather to a a grandson to avoid double death duties. But the crucial difference is that this usually happens with the consent of all parties and the judge merely has to give assent. Here, the Marquess of Blandford is highly likely to contest the attempt to take away his birthright. Mr Morton predicts a 'full-blown, knock-'em-down struggle'. Proceedings have already been instigated in the Chancery Division by solicitors acting on the duke's behalf. Bleak House looms.
The legal ground for the family's case is believed to be section 64 of the Settled Land Act, where the trustees will argue it would not be in the interests of the 'tenantry and peasantry' of the estate for Jamie to inherit.
Given by Queen Anne and a grateful nation to John Churchill, the 1st duke and victor of the battle of Blenheim, the palace and its estate is very much an economically viable proposition, and the 11th duke, 67, who has made it his life's work, wants it to stay that way. It is now a large business with a turnover of more than pounds 2m a year, a boating lake, inflatable castle and gift shops, with every penny from visitors ploughed back into the fabric.
Much of the legal argument in the case is likely to centre on the prognosis for Jamie Blandford's future behaviour. On his past record it can hardly be favourable.
Where his peer group from Harrow have extended their curricula vitae with degrees, works published, or caps won for England, he has clocked up a string of fines for assaulting police, speeding, driving while disqualified, breaking into a chemist's in search of drugs, possession of cocaine and non- payment of maintenance to his estranged wife, Becky, the Marchioness of Blandford. He has served three prison sentences, but none seems to have acted as the salutary lesson the magistrates must have intended. The family motto could have been designed for him: Fiel pero desdichado (Faithful though unfortunate).
His past behaviour is characteristic of a drug addict from any walk of life. Addicts rarely give up until they themselves recognise the need to do so. Jamie Blandford appeared briefly to have reformed when he married, then relapsed. He has lied consistently, borrowed money from friends and family, and bounced cheques for everything from pianos to electric carpet cleaners.
According to Chief Inspector Richard Miles of the Metropolitan Police, who has just completed a secondment to the Institute for the Study of Drug Dependency and sent a report on the cocaine market in the UK to the United Nations, drug users like to demonstrate their street wisdom by conning others - hence the deceits and bounced cheques.
Dealers would be unlikely to let go a milch cow as productive to them as Blandford, who always seems to have been able to get his hands on money.
Ch Insp Miles knew of one wealthy addict who stopped taking drugs, so the dealers pushed it through his letter box, where he could not resist the temptation. Next day they came round for their payment, and the cycle continued.
In court yesterday, Blandford's lawyer said Blandford was being 'helped considerably at the moment' as a result of treatment he was undergoing - understood to be at a pounds 300-a-night clinic in Harrow, north London. He intended to continue the treatment, he said.
In 1882 Gladstone remarked: 'There never was a Churchill from John of Marlborough that had either morals or principles.' The present Duke appears to be an exception to the rule, and he clearly hopes his second son is another one.