An undercover investigation filmed by ITV's Exposure reveals how a worker at the Nigeria High Commission (NHC) claimed he could transport items, including stolen art, out of "any airport" using his diplomatic connections.
Posing as a criminal gang, the Exposure team, led by reporter Mark Williams-Thomas, met Alfa Abutu, in a London hotel. Abutu told them that he could transport their stolen art to Paris.
"Give me your suitcase, this suitcase usually has to be wrapped with the national flag before we can move it anywhere. And we use diplomatic vehicle whereby the police authorities will not stop us," Abutu said.
Exposure later told Abutu the art was worth nearly £1 million, to which he suggested a commission of £250,000. In a series of meetings with undercover reporters, Abutu also claimed he could help transfer money, and smuggle diamonds and gold out of the country using an embassy car and its associated privileges.
"The easiest way is that, let's say this box is loaded with $1 million and they are going out with it or gold, or diamond. With my link, we use a diplomatic vehicle from here straight to Heathrow or Gatwick," he said.
"They will not open the box they are bringing out. It's not a problem."
When asked to comment on Exposure's findings, Abutu denied any wrongdoing and said he had never been involved in criminal activities. He said he is local staff, not a diplomat, doesn't have diplomatic immunity and couldn't have assisted the Exposure team to move an item.
He said he believed Exposure's undercover reporter was not genuine but decided to play along with him.
Following the revelations, the Nigeria High Commission immediately suspended Abutu from his position in the accounts department, where he had worked for six years.
Spokesman Ahmed Inusa said:
During its investigation, Exposure uncovered that while Abutu did have diplomatic links, he was not a diplomat and his claims of diplomatic immunity were false.
Nevertheless, the Nigerian High Commission says it "utterly condemns Mr Abutu's conduct".
The Commission told Exposure that Abutu "tried to fool investigators into believing that he is [a diplomat] for personal financial gain." The Commission also said that he does not have access to the diplomatic bag.
"As soon as the High Commission became aware of Mr Abutu's conduct, he was suspended as part of the Mission's internal disciplinary procedure," spokesman Ahmed Inusa said. The Commission said Abutu's conduct was entirely personal and nothing to do with them.
The case has provoked concern that diplomatic privileges are open to widespread abuse - whether via smuggling contraband in and out of the UK, or using immunity to evade criminal prosecution.
Labour MP Fiona Mactaggart co-chairs the all-party Parliamentary Group on Human Trafficking and has lobbied on the issue of diplomatic staff who abuse their positions in Britain.
Speaking to reporter Mark Williams Thomas, Ms Mactaggart said Abutu's claims were "really shocking":
Diplomats: Above the law?
While Abutu lied about his diplomatic immunity, many of the 22,000 foreign diplomats and embassy workers resident in the UK do have full immunity from prosecution.
Immunity is bestowed by the United Nations Vienna Convention 1961, an international treaty which defines a framework for diplomatic relations. It gives diplomats certain privileges, which allow them to operate in their host country without fear of coercion.
However, Exposure's investigation reveals how some diplomatic workers use - and in some cases abuse - their special privileges to evade being arrested or charged with serious crimes, including assault, drink driving, human trafficking, and domestic enslavement.
It also highlights how the sanctity of the diplomatic bag - the fact that it cannot be searched - makes it a valuable asset for international criminals.
Former Irish diplomat Eamon Delaney told Exposure that during his eight-year placement in the US, he was aware of diplomatic bags being used by other countries to transport illegal items:
And leading QC Geoffrey Robertson told Exposure, "I have had evidence in cases that I have done where diplomatic bags have been used by some members of embassies to smuggle guns, arms, murder weapons, certainly drugs into countries."
But diplomatic bag abuse may be just one way that embassy staff evade the law.
Exposure analysed Foreign Office statistics concerning alleged offences committed by diplomats between 2007 and 2012. The analysis showed that there were 88 alleged "serious" offences committed by diplomats during this time period.
Top of the table is Saudi Arabia with 11 alleged offences, followed by Kazakhstan and Russia with five, Cameroon with four and the Ivory Coast and Ghana with three each. The Saudi embassy told Exposure that serious action is taken against any diplomat found to have broken UK laws.
Most of the 88 alleged offences relate to driving, but others include sexual assault, human trafficking, actual bodily harm, threatening to kill and robbery. Of the 11 offences allegedly committed by Saudi diplomats, two concern human trafficking while one alleges sexual assault.
Former diplomat Eamon Delaney believes that diplomatic immunity is becoming out of control, "There's no need for so many diplomats and so many staff of embassies to walk around with immunity and with Diplomatic Passports: It's an indulgence, it's outdated, and it is a license to abuse."
Exposure: Inside The Diplomatic Bag is broadcast tonight at 10:35pm on ITV.