A BRITISH court sentenced the former governor of a Nigerian oil state to 13 years in prison on Tuesday after he pleaded guilty to embezzling £50m (R626m) in one of the biggest money-laundering cases seen in Britain.

A founding member of Nigeria's ruling party, James Ibori is the most prominent Nigerian politician to be prosecuted for the corruption that has held back Africa's top oil producer for decades.

He pleaded guilty to 10 charges of fraud and money-laundering committed during his eight years as governor of Delta State, an impoverished maze of mangrove creeks and pipelines ravaged by years of armed conflict over access to oil money.

"During those two terms (as governor) you turned yourself in very short order indeed into a multi-millionaire through corruption," Judge Anthony Pitts told Ibori at Southwark Crown Court in London.

Pitts said it was one of the biggest money-laundering cases seen and that the £50m Ibori had admitted to stealing might be a fraction of his total booty.

"The figure may be in excess of £200m, it is difficult to tell. The confiscation proceedings may shed further light."

Prosecutor Sasha Wass said Ibori engaged in a wide variety of frauds. The single biggest scam involved siphoning off $37m in fake consultancy fees during the sale of Delta State's stake in mobile telecoms company V Mobile.

The court heard that Ibori used his stolen fortune to acquire six foreign properties, a fleet of luxury cars including a Bentley and a Maybach 62, and that he tried to buy a jet.

His properties include a country mansion in a village in southwest England, close to the private school where his three daughters are being educated.

His defence counsel, Nicholas Purnell, argued that his crimes were mitigated by his achievements as governor, particularly the construction of vital infrastructure.

In a bizarre courtroom twist, Purnell called former Wimbledon footballer John Fashanu, now Nigeria's ambassador for sports and tourism, as a character witness.

Fashanu praised Ibori for overseeing the construction in Delta State of three Olympic and Fifa-registered stadiums, a golf course and shooting range.

Britain was the destination of choice for generations of corrupt Nigerian politicians looking to spend their money on houses or luxury goods. Ibori's jail sentence may put an end to that.

Ibori's criminal career started in 1991 when he was working as a cashier at Wickes, a home improvements chainstore in London, and was caught stealing from the till. In 1992, he was convicted again, this time for handling a stolen credit card. He returned to Nigeria and became involved in politics.

In 1999 he was elected governor of Delta. Ibori established himself as a behind-the-scenes kingmaker within the ruling People's Democratic Party. This ensured that he remained influential after stepping down in 2007.

He was also able to obtain a court order that prevented the London Metropolitan Police from visiting Delta State in October 2007 to gather evidence.

In April 2010 Ibori fled to Dubai, where he was arrested. He was extradited to London in April 2011 .

Ibori is likely to spend four-and-a-half more years behind bars because he has already been in custody for two years, and because he will be eligible for parole halfway through his prison term.