The BBC has seen evidence that top executives at Shell knew money paid to the Nigerian government for a vast oil field would be passed to a convicted money-launderer.
It also had reason to believe that money would be used to pay political bribes.
The deal was concluded while Shell was operating under a probation order for a separate corruption case in Nigeria.
Shell said it did not believe its employees acted illegally.
OPL 245 is an oilfield off the coast of Nigeria whose estimated nine billion barrels of oil are worth nearly half a trillion dollars at today’s prices. Shell has been active in Nigeria for nearly 60 years and was keen to acquire the field.
New evidence shows just how far Shell was prepared to go to get its hands on it.
Standing between Shell and its prize was Dan Etete, whose company acquired the rights to OPL 245 for a tiny sum while he was oil minister of Nigeria. He was later convicted of money laundering in a different case.
Shell and the Italian oil company ENI eventually acquired OPL 245 in 2011 – by paying $1.3bn to the Nigerian government.
The government promptly passed on more than $1bn of the money to a company called Malabu, which was controlled by Dan Etete.
Emails obtained by anti-corruption charities Global Witness and Finance Uncovered, and seen by the BBC, show that Shell representatives were negotiating with Etete for a year before the deal was finalised.
In March 2010, an email from a former MI6 officer employed by Shell shows the company believed Etete stood to benefit from the deal.
“Etete can smell the money. If, at 70 years old, he does turn his nose up at 1.2 bill he is completely certifiable and we should then probably just hold out until nature takes its course with him.”
That email was forwarded to the then Shell chief executive Peter Voser – one of the most powerful men in the oil business – showing knowledge of Etete’s involvement went right to the top.
Representatives of Peter Voser declined to comment.
Shell also had good reason to suspect that hundreds of millions would end up in the pockets of Nigerian politicians including the former President Goodluck Jonathan.