Romy Andrianarisoa, 47, is accused of seeking substantial payments from Gemfields between 2021 and 2023 to help the company expand its business into Madagascar.

Andrianarisoa has pleaded not guilty to one count of bribery.

Prosecutor Alex Leach told jurors at Southwark Crown Court that Andrianarisoa was, at the time of the alleged offending, a "trusted adviser" to Rajoelina.

Leach said that in 2021, Andrianarisoa met with senior Gemfields staff including CEO Sean Gilbertson, who is expected to give evidence, about the possibility of mining in Madagascar.

At the meeting, Andrianarisoa "made it clear she had direct influence on the president", Leach added.

He said Gemfields later approached Britain's National Crime Agency (NCA) after it became clear Andrianarisoa and her associate Philippe Tabuteau were seeking a bribe.

The NCA then deployed an undercover officer posing as a consultant negotiating on Gemfields' behalf, the prosecutor said.

"In the meetings that followed, the undercover officer recorded Romy Andrianarisoa and Philippe Tabuteau asking for bribes in return for using their influence to arrange mining rights in Madagascar," Leach said.

According to the indictment, Andrianarisoa and Tabuteau allegedly sought around 270,000 Swiss francs ($310,000), plus a 5% stake in a Gemfield company mining in Madagascar.

Tabuteau is not on trial.

(Reporting by Sam Tobin; Editing by Bernadette Baum)

By Sam Tobin