A Cayman Court has ordered Maan Al-Sanea to pay the Algosaibi family $2.5 billion, the latest twist in a tortuous legal battle the Saudi billionaire and his in-laws have been waging in courts across the globe since 2009.

The judgement will allow the family to go after the money, though it is unlikely to be the final word on the rift in the clan, which has left some of the world's biggest banks nursing billions of dollars in losses.

"It puts us in a very strong position to go against Maan al-Sanea and use those assets to reach commercial solutions with the banks," said Eric Lewis, the Algosaibis' main lawyer.

The Algosaibis are accusing Al-Sanea - who married into the family 30 years ago - of siphoning off billions of dollars to his own business empire, the Saad Group, after he was put in charge of the Algosaibis' financial arm.

They say this exonerates the Ahmad Hamad Algosaibi & Brothers (AHAB) partnership from liability for claims from creditors that came in when the family's financial empire collapsed in 2009, alongside that of Al-Sanea.

Al-Sanea has always categorically denied these allegations. His spokesman declined to comment.

The two Saudi families have been exchanging blows in a complex legal battle in London, New York, Bahrain, Switzerland and Saudi Arabia ever since.

AHAB's claim for dishonest breach of fiduciary duty by Al-Sanea was now proven, the Cayman Court said.

The ruling makes it more likely that Al-Sanea would at last make a detailed case in his defence in the Caymans. So far, he has only contested the jurisdiction of the British overseas territory without arguing the merit of the case.

The interim damages can be claimed for "a reasonable proportion of the damages which in the opinion of the Court are likely to be recovered," the Algosaibi family said. The family's total claims are in the order of $9.2 billion.

"All questions going to quantification ... remain open to be challenged at the final damages hearing," the ruling said.

Virtually all of Al-Sanea's assets are in Saudi Arabia, which is a no-go area for foreign creditors.

AHAB will also need to replead its case using new evidence - found in a cupboard belonging to Saud Algosaibi during a trial in London last June - which had derailed its argument it wasn't liable for claims put in by five banks.

"A party should not expect to rely upon a pleaded case which it acknowledges even if only in part, to be factually incorrect," the ruling, dated June 12, said.

AHAB confirmed that it would replead its case.

Losing the London case only a few days into a trial that was scheduled to go on for weeks was a blow for the Algosaibi family, who then also saw a world-wide freezing order against Al-Sanea's assets lifted in the Cayman islands.  - Reuters