The Ritz casino has won a High Court battle to recover £1 million on unpaid cheques from a wealthy gambling addict.

The "high end" casino in London's Piccadilly took legal action against Mrs Noora Abdullah Mahawish Al-Daher - known to western acquaintances as "Nora"- after she gambled and lost £2 million on the evening of April 3, 2012.

Mrs Al-Daher, whose husband is the foreign minister of Oman, argued that the Ritz's claim against her could not succeed because it was based on "illegality" and the unlawful giving of credit.

She also asserted that the casino had been "under a duty of care" towards her as its staff knew she was a gambling addict or problem gambler and should have restrained her from betting.

Her lawyers argued signs of her addiction were apparent both through how much she gambled in the period leading up to that evening, and on the evening itself, and by what she said.

But High Court deputy judge Seys Llewellyn QC ruled today there was no legal authority that supported her case and gave judgment to the casino "in the sum of £1m, as claimed", plus interest.

He declared: "I hold that there was no unlawful giving of credit to Mrs Al-Daher."

On the question of a duty of care, he said: "In my judgment authority does not support such a duty."

The judge said he had no doubt that, if Mrs Al-Daher had been refused permission to carry on gambling at the Ritz casino, she "would have been eager and inclined to gamble at other casinos thereafter, and very probably during her stay in London during the days or weeks after 3 April 2012."

The judge added: "It is striking that she and her family gambled away 5m US dollars in Las Vegas in June some two to three months later."

Judge Llewellyn rejected Mrs Al-Daher's counter-claim to recover the £1m of her debt she had paid in December 2012.

The judge described her as "a woman of great wealth". He said it came from family funds in Saudi Arabia from her late father, whilst her husband was wealthy in his own right from business interests in Oman, and worldwide through a Saudi Arabian conglomerate.

On the evening she lost the £2m she had signed and given individual cheques for £200,000 and £300,000 in return for gambling chips.

The judge said it had been her habit to sign cheques to the casino in such sums, but the cheques signed that evening were dishonoured.

In December 2012 she paid £1m to the casino but left £1m outstanding and it was that amount the casino was entitled to recover.