Georgy Urumov, 37, was jailed for 12 years and Vladimir Gersamia, 33, for seven years after being found guilty of multiple fraud offences following a four-month trial at Southwark Crown Court.

The first part of the fraud was carried out in 2011, prosecutors said.

Urumov joined the Russian-owned company Otkritie Securities Ltd (OSL) and manipulated the firm into paying him approximately 20 million pounds under the false impression that it would be distributed to others also joining the firm.

In the event, Urumov held on to the vast majority of the money, the Crown Prosecution Service (CPS) said.

Urumov committed more offences by trading Argentine debt products and fooling his employer into believing that they had been bought at four times their true cost, the CPS said.

He then pocketed the difference and transferred the gains to bank accounts out of the UK.

Urumov used Gersamia, an employee of investment management firm Threadneedle Asset Management, to help cover his tracks.

The CPS said the men had stood to gain another 121 million pounds from their activities.

Detective Superintendent Maria Woodall of City of London Police said the defendants were respected figures in their industry. "They went to great lengths to try and launder the money by using the international banking system," she said in a statement.

CPS Specialist Prosecutor Alistair Dickson said: "Due to the international scale of this fraud, the prosecution team considered millions of pieces of evidence and made arrangements to call witnesses from across the world in order to present a compelling case to the jury."

Otkritie Holding Chairman Alexey Karakhan said in a statement that his group was working with law enforcement authorities in other countries, including Switzerland, Israel and Russia to pursue others involved in the fraud.

"We are more than satisfied with the jury’s verdict and the strong message sent by the lengthy prison term given to Urumov," he added.

"From the outset we pledged to do everything possible to ensure that justice would be done and that the fraudsters would be held responsible for their heinous conduct. This verdict completely vindicates our approach."

(Reporting by Stephen Addison; editing by Michael Holden)