The man claiming that one of J K Rowling's Harry Potter books was lifted from another work has been ordered to pay more than £1.5m (€1.7m) into court as security for the costs of the author and her publisher - or the case will be struck out.
The order was made by Mr Justice Kitchin at a hearing in the Chancery Division of the High Court.
The claim has been brought by Paul Allen, trustee of the estate of the late Adrian Jacobs, who died in 1997, who alleges that the fourth Harry Potter book, 'Harry Potter and the Goblet of Fire', was plagiarised from Mr Jacobs' book, Willy the Wizard.
Mr Allen is suing Ms Rowling and her publisher, Bloomsbury, for some £5m (€5.74m).
Mr Justice Kitchen last year rejected an application by Ms Rowling and Bloomsbury to strike the case out - although he said it had only an "improbable" chance of success.
Now he has ordered Mr Allen to make a series of staged payments into court as security for 65% of the costs faced by Ms Rowling and Bloomsbury.
He said Mr Allen should pay £322,691 (€370,525) for Bloomsbury's costs and £571,613 (€656,346) for Ms Rowling's costs by April 21, with a further £24,650 (€28,304) for Bloomsbury's costs and £178,441 (€204,892) for Ms Rowling's costs to follow by August 5.
The final payments - £129,373 (€148,530) for Bloomsbury's costs and £318,975 (€366,207) for Ms Rowling's - must be made by November 11.
The judge said failure to make any of the payments into court by the specified time would lead to the claim being struck out and Mr Allen being ordered to pay all the defendants' costs of the action.
Ms Rowling had described the claim that her book was copied from Willy the Wizard as "not only unfounded but absurd", and said she had never even seen the book until the claim was launched in 2004.
Mr Justice Kitchin said that while Mr Allen's claim was not so bad as to be fanciful, it was improbable that it would succeed - and the chances of success were so poor that the court was justified in exercising its discretion to make an order for payments as security for the defendants' costs, according to the Lawtel legal reporting service.
Mr Allen, the judge said, was a nominal claimant since he had no personal connection with the dispute over copyright, no role in raising funds to pursue litigation, and no final interest in the outcome of the claim.
There was reason to believe that he would not be able to pay all the defendants' costs if he had to.
In addition, nearly six years had passed between the original copyright infringement suggestion and the launch of the case, and there had been no explanation for the delay.
The court had earlier held that many parts of Mr Allen's claim could not be sustained, but he had done nothing to change the claim, and was therefore still carrying on with elements which the court had already rejected.
In addition, Adrian Jacobs' son, Jon Jacobs, to whom copyright in Willy the Wizard was assigned, was the obvious beneficiary of the claim as he was the only beneficiary of his father's estate, had substantial means, and should be able to provide the security for costs sought by Ms Rowling and the publisher, Lawtel reported.
The case is set down for a 10-day trial in February next year, assuming the payments into court are made.
The order is a second major setback for Mr Allen in the claim. In January it was comprehensively rejected by a judge in United States District Court in New York.
Judge Shira Sheindlin, sitting in the Manhattan-based District Court for the Southern District of New York, said "the contrast between the total concept and feel of the works is so stark that any serious comparison of the two strains credulity".
In that case Mr Allen, for Mr Jacobs' estate, had sought to sue Ms Rowling and her American publisher, Scholastic.
A spokesman for Mr Allen said after Judge Sheindlin handed down her decision on January 4 that the estate's US lawyers were studying the decision with a view to launching an appeal.
But Mr Allen pledged then, in a statement issued by an Australian-based PR firm, that the action in the High Court in London would go ahead.