She said she had been notified of the existence of a similar letter in 2011, shortly after the former prime minister opened his bank account in 2011.

The four letters suggested that the “prince” would extend a “donation” to Najib, she said.

“They were just letters of intent and promise. They did not disclose details of the actual transactions,” Zeti told the High Court hearing Najib’s 1MDB corruption trial.

The court had previously heard testimony from former relationship manager Joanna Yu that fugitive businessman Low Taek Jho had instructed AmBank to keep the existence and contents of the four letters confidential.

Earlier, Zeti told the court she was made aware that Najib had opened an account with AmBank in 2011.

She said AmBank’s then managing director Cheah Tek Kuang had informed her of the opening of the account at a meeting in 2011.

Cheah, who testified last year, said that it was important to notify the central bank’s governor of the matter as the then prime minister was a “politically exposed person”.

In her testimony today, Zeti said AmBank was not obliged to inform the central bank about the opening of the bank accounts.

She said there was no legal or policy obligation in place requiring banks to inform BNM about their account holders.

“Everyone can open an account (at any bank). The financial institution is supposed to do its due diligence (on the customer) to check if everything is in order.

“Even if it (the documentation) is not in order and the account is opened, BNM would not be informed,” said Zeti when questioned by deputy public prosecutor Kamal Bahrin Omar.

The hearing continues before Justice Collin Lawrence Sequerah on Aug 14.

Najib is standing trial on 25 charges of abuse of power and money laundering of alleged 1MDB funds of RM2.28 billion deposited into his AmBank accounts between February 2011 and December 2014.