Rowland Nakanda, 54, was caught up in the corruption trial of his brother-in-law James Ibori, the former governor of Delta State in Nigeria between 1999 and 2007.

After the ex-governor and his wife Teresa, Nakanda's sister, were jailed for 18 years for fraud and money laundering in 2012, Nakanda and his wife became the guardian of the couple's three children.

Police began investigating the former Royal Mail worker’s financial activities after they discovered the children were being educated at a private school in the UK.

CCTV footage showed him paying £15,000 in cash for school fees at his local Lloyd’s bank in Grays, Essex, Southwark Crown Court heard.

Jailed: James Ibori, a former Wickes cashier who committed a series of scams while a Nigerian state governor Detectives later found £350,000 in unexplained cash deposits in his accounts, jurors were told.

Nakanda, of Tyne Gardens, South Ockendon in Essex, denied two counts of money laundering but was convicted after a month-long trial.

He was acquitted of cheating the Revenue. He was jailed for two and half years today, while his wife Chifu was acquitted of all charges.

Rupert Broad, formerly a Detective Inspector in the Met’s Proceeds of Corruption Unit, said: “Rowland Nakanda previously worked for the Royal Mail and lived a modest lifestyle with his wife in Essex.

"I am pleased that we were able to demonstrate that Nakanda knew that the money he was dealing with was the proceeds of criminal conduct and had originated from James Ibori’s corrupt activity during his governorship of Delta State.

"This sentence should act as a warning that we will go after everyone involved in fraudulent activity, however complex and wide-reaching the fraud."

James Ibori, who began his working life as a £5,000-a-year cashier at a Wickes DIY branch in Ruislip, became a multi-millionaire after returning to his homeland and committing a series of scams during an eight-year career running its oil rich Delta State.

His wealth allowed him to buy expensive homes, a £12 million jet and a £1 million fleet of cars including a Bentley, Mercedes and armoured Range Rovers. A decision on how much he will have to repay has been postponed until June next year.