LLOYDS TSB is under seige from an international team of investigators claiming that it should repay a large part of $242 million (£132 million) stolen from a bank in Brazil and allegedly laundered through the UK bank’s Swiss division.

Forensic lawyers hired by the South American bank have spent five years following the trail of the stolen money in an inquiry that has spanned four continents, involved the apparent assassination of one of the accused, and led to the arrest and imprisonment of four of the accused.

The UK bank faces accusations that it allowed nearly a third of the proceeds from the $242 million heist at Brazil’s Banco Noroeste to be laundered through its private bank in Zurich.

A key part of the case being brought by disgruntled shareholders in Banco Noroeste finally reached the Swiss courts this week. Lawyers gathered in Geneva to hear the testimony of Naresh Asnani, a British citizen and former Lloyds TSB customer, who has been in custody in Switzerland for more than a year.

Mr Asnani stands accused of laundering $122 million on behalf of Emmanuel Nwude Odinigwe and Ikechukwu Christian Anajemba, two Nigerian nationals and the alleged masterminds behind the theft.

Mr Anajemba is now dead — apparently murdered. Mr Odinigwe is in jail in Lagos, as is Amaka Anajemba, Christian’s widow, also accused of involvement in the theft.

The three are thought to have spent the money on buying millions on items including a $500,000 bullet-proof Mercedes, and “his and hers” diamond-encrusted Rolex watches. Mr Odinigwe is also accused of using $9 million to buy a board position on the Union Bank of Nigeria. The equivalent of £120,000 was even allegedly offered as a bribe — in carrier bags bearing the slogan “Ghana Must Go” — to Nuhu Ribadu, the chairman of Nigeria’s financial watchdog, which he refused.

The British bank together with Citibank, of the US, is accused of allowing money to be laundered in accounts set up by Mr Asnani, who claimed to have legitimate business reasons for funnelling millions of dollars back to Mr Odinigwe in Nigeria.

Although Mr Asnani this week recanted in court on an earlier admission that he had laundered money through his Lloyds TSB account, Banco Noroeste’s lawyers are claiming that lax controls at the British and American banks helped to ease the flow of money back to Nigeria.

Legal documents used to back the claim appear to show that far from being a sophisticated scam involving a series of bogus accounts, the scheme was in fact very simple. It seemed to rely on a personal relationship between a business associate of Mr Asnani and Rolf Wasmer, the Lloyds TSB banking official who was in charge of running the account.

In 1995, the business associate introduced Mr Asnani to Mr Wasmer — the former was finding that his existing bank was inflexible over US dollar transfers. At the time, companies importing goods in to Nigeria were suffering because of tight foreign exchange controls.

Companies had to pay for foreign imports in American dollars but received payment for them in Nigerian naira. There was no easy way for the Nigerian currency to be exchanged back in to dollars, aside from on the black market.

Mr Asnani, an importer of electronic goods, opened up his business account with Lloyds TSB in July 1995. Court documents claim that in September he began to receive large sums of money that had been transferred from Banco Noroeste’s Cayman Island division via a group of banks based in New York. Nearly $30 million was allegedly transferred before the end of the year alone, with a further $46 million believed to have followed until the account’s eventually closure in May 1997. A series of written exchanges between Mr Wasmer and his bosses at Lloyds TSB’s London headquarters appear to show that the Swiss bank manager was happy to accept Mr Asnani’s explanations for the huge sums of money that were moving in and out of the bank.