As part of BBC World Service's series on Intercontinental Cops, Jenny Chryss explores how investigators from London and Lagos have linked up to combat corruption and fraud in Nigeria.
Cooperation between Scotland Yard and Nigeria has improved
Globally, Nigeria has become associated with what is known as "advance fee" or 419 fraud.
Virtually anyone with an email account will be familiar with this crime, which involves sending emails or faxes to potential victims around the world, sucking them into a highly attractive but utterly false financial deal.
Back in Nigeria, the rewards are potentially highly lucrative - but now, owing to a crackdown and much-improved co-operation between police forces globally, it has become more risky for the perpetrators.
"Historically we've always had a problem getting evidence from Nigeria, but that's changing," says Detective Sergeant Mark Radford, head of the Africa desk at New Scotland Yard.
"They're keen to co-operate and bring a lot of the criminals in Nigeria to justice."
At the holding cells in the centre of the country's commercial capital, Lagos, more than 50 suspects are waiting for court appearances on 419 charges. It is a busy place.
Recently Nigeria has, for the first time ever, begun a major crackdown on all sorts of economic crime - and it is needed.
Last year it was ranked the sixth most corrupt country in the world - and that was its best rating ever.
Now, though, internet service providers who allow online fraudsters to operate will face criminal charges, while decades in jail await the scammers themselves - with little chance of early parole.
Still, with rich pickings still to exploit, Nigeria's criminals will not give in easily.
As well as the most well-known scams, others are now coming into vogue. In one - the so-called "black money" scam - people are shown what appear to be bank notes which have been dyed.
The scammer appears to show how to remove the dye, and sells the "notes" for cash. In fact, the notes are worthless waste paper.
To give credence to their operations, the warehouses and hotels Nigerians use as meeting places are usually in European cities, with London being a favourite.
Olaolu Adegbite, head of the Economic and Financial Crimes Commission's Advance Fee Fraud section in Lagos, said one man from the US had ended up paying $2.1m after been conned in this way.
"The gentleman got convinced when he arrived in the UK and the men were well-dressed, some black, some white, and looked responsible," he said.
"He was convinced, he was carried away."
In this case the fraudster was eventually caught in Nigeria and sentenced to 342 years in jail. He must also repay the $2.1m in full.
But there is a long way to go. Allegations of corruption go to the very highest level.
London detective Peter Clark has been trailing one Nigerian state governor, suspected of corruption in Nigeria and money-laundering in London, since January 2004.
Only when he began delving into what initially was a credit card fraud case that he realised how significant it might prove to be, when it became apparent that millions of pounds had been secretly moved from Nigeria into London banks.
For years, widespread corruption has been blamed for many of Nigeria's ills. Schools, hospitals and public services are falling far short of what could be expected of a country that is oil-rich and, in many areas, highly fertile.
And there is now growing evidence that the people living in Nigeria's poor Plateau state are worse off than they should be, because, it is alleged, the governor has siphoned off millions of pounds from the public purse.
Accusers say corruption makes Nigerian states poorer
Specifically, it is claimed he redirected at least £6m meant for environmental improvements into his own bank accounts.
"Every so often states make a bid to the federal government for extra works within their state - and what we've been able to find out is that as a result of cheques being issued for that work, the state governor basically steals that cheque," detective Clark said.
"We've identified that portions of that cheque have found their way into London bank accounts."
However, the governor of Plateau continues to rule because the assembly here has elected to keep him in office, where he has immunity from prosecution.
Although he declined to be interviewed by the BBC, the speaker of the assembly, Simon Lalong, told us the money allocated to Plateau state had been properly spent.
"We invited the EFCC to come and prove the allegations - because what we had at first was just paper telling us this is the bundle of allegations against his Excellency, including the jumping of bail," he said.
"They wrote and said this is the allegation, but we said, 'what are the facts?'"
In Nigeria it is being reported that 24 of the country's 36 state governors are now under investigation.
Allowing these men to go free is not an option for the EFCC chairman Nuhu Ribadu.
"If this country is going to change, if anything is going to work, we have to fight corruption, we have to establish the rule of law and order," he says.
"We cannot do it alone, because we are fighting the power, the authority, those with the money, and we need those who are good, who understand the need of such things to stand by us."