A Swiss lawyer, Enrico Monfrini says he has been working for the past twenty years to recover funds looted by the Sani Abacha government.
Speaking to the BBC, Mr Monfrini said he was first contacted by the civilian government of President Olusegun Obasanjo to help with the recovery.
He also explained some of his findings on how the former military dictator diverted the funds to Swiss banks using several allies and what he describes as dollars by truckloads.
In 2008, Mr Monfrini said $508m found in the Abacha family’s many Swiss bank accounts was sent from Switzerland to Nigeria between 2005 and 2007.
According to him, by 2018, the amount Switzerland had returned to Nigeria had reached more than $1bn.
He alleged that the late dictator diverted over four to five billion dollars at the initial stage.
Mr Monfrini said he is still expecting $30m he says is sitting in the UK to be returned, along with $144m in France and a further $18m in Jersey.