* Businessman on trial in UK over alleged Bahrain bribery
* Court sees letter from Bahraini deputy prime minister
* Witness says Serious Fraud Office not swayed by letter
* Sensitive trial comes at time of unrest in Bahrain
By Estelle Shirbon
LONDON, Dec 5 (Reuters) - A deputy prime minister of Bahrain sought to intervene in a British bribery prosecution by writing to the head of the Serious Fraud Office (SFO) and to the British government's legal adviser, a London court heard on Thursday.
Lawyers said Jawad bin Salem al-Urayed wrote about the case of Victor Dahdaleh, a businessman accused of paying some $67 million in bribes to former managers of Aluminium Bahrain (Alba) in return for a cut of contracts worth over $3 billion.
One of Britain's biggest bribery trials for years, the case involves allegations of corruption at senior levels of government and business in Bahrain, a sensitive issue at a time of political unrest in the secretive Gulf kingdom.
British-Canadian national Dahdaleh has pleaded not guilty to eight charges brought by the SFO relating to events between 1998 and 2006 at Alba, the world's fourth-largest aluminium smelter which is majority-owned by the Bahraini state.
Reuters was unable to contact Urayed, one of five Bahraini deputy prime ministers, for comment on the letter, which was read out in court by Dahdaleh's lawyer Nicholas Purnell. The prosecution did not dispute the authenticity of the letter, addressed to the SFO director and the Attorney General.
"At the request of Allen & Overy (the London law firm then acting for Dahdaleh), we hereby confirm that the board of directors of Aluminium Bahrain knew of and approved all contracts entered into by Alba, including knowing of and approving payments made by Victor Dahdaleh," the letter said.
"This was entirely in accordance with Alba practice," it added.
Those assertions are highly relevant to Dahdaleh's defence, which is that he had "principal's consent" for the payments he made to then Alba chairman Sheikh Isa Bin Ali Al Khalifa and to then chief executive Bruce Hall.
Dahdaleh is charged under an old anti-bribery law from 1906 which says that payments are not corrupt if they are made by an "agent" on behalf of a "principal" who consented.
The SFO's position is that the rightful principal was the board of Alba and that it never approved the payments.
Sheikh Isa, who is named as a co-conspirator in the indictment but is not taking part in the trial, has denied any wrongdoing in a statement issued by a Paris-based lawyer.
Hall has pleaded guilty to a charge of conspiracy to corrupt and accepted that he was part of a criminal conspiracy with Sheikh Isa and Dahdaleh. He is cooperating with the SFO.
Purnell put Urayed's letter to the SFO's case officer, Sasi-Kanth Mallela, who was appearing as a witness on Thursday.
"This letter is capable of being read in a number of ways ... It doesn't mention the payments to Sheik Isa and Bruce Hall," Mallela said, adding that it did not explain how Urayed could have detailed knowledge of the affairs of the Alba board.
Mallela said he had received assurances from Alba's lawyers at U.S. firm Akin Gump that Urayed was not in a position to make such assertions about who knew or approved of what at Alba.
Mallela had later written to Allen & Overy to say that the letter had not changed the SFO's position as it did not explain how Urayed knew what he said he knew, nor did it indicate that he was prepared to be interviewed about the issue by the SFO.
It is not the first time an SFO investigation into alleged corruption in the Gulf has come under political pressure.
In 2006, a probe into a huge arms deal between British defence group BAE Systems and Saudi Arabia was dropped after the British government told the SFO it risked damaging national security interests. (Additional reporting by William Maclean in Bahrain; Editing by Andrew Heavens)