Sani Abacha, who ruled Nigeria from 1993 to 1998, is believed to have stolen up to £3billion ($4billion) during his time in office, some of which he stored in Swiss accounts - the neutral nation has already handed over $700million of the dubbed “Abacha loot” to the government of Nigeria in the last decade.

In a statement, the Swiss government said: “In keeping with its policy of returning illegally acquired assets, Switzerland has reached an agreement with Nigeria and the World Bank on the restitution of approximately $321 million to Nigeria's population.

“The modalities of restitution are set out in an agreement which was signed by the three parties on 4 December in Washington DC at the Global Forum on Asset Recovery (GFAR).

“Director of the Directorate of International Law and Head of the Swiss delegation to the GFAR, Ambassador Roberto Balzaretti, signed the agreement together with Nigerian Justice Minister Abubakar Malami and Head of the World Bank representation in Abuja, Rachid Benmessaoud.

“The agreement, negotiated for Switzerland by Ambassador Pio Wennubst, Assistant Director General of the SDC, stipulates that the restitution of funds will take place within the framework of a project supported and overseen by the World Bank.

“The project will strengthen social security for the poorest sections of the Nigerian population. The agreement also regulates the disbursement of restituted funds in tranches and sets out concrete measures to be taken in the event of misuse or corruption.

“The chosen solution for restitution is being undertaken by the three contracting parties as a partnership.

“It is in line with the objectives of Switzerland's strategy to freeze, confiscate and return the illicitly acquired assets of politically exposed persons (asset recovery) and is based on the principles of transparency and accountability as well as the involvement of civil society in the restitution process.

“These assets, which were initially frozen in Luxembourg, were repatriated and confiscated by Switzerland as part of criminal proceedings brought by the public prosecutor's office of Geneva against Abba Abacha.

“At its meeting on Friday, 1 December 2017, the Federal Council approved the signing of the agreement.”

The money was frozen in 2014 by a Swiss court following a legal procedure against the former ruler’s son, Abba Abacha.

The Nigerian government also made a statement, claiming the country would continue in its mission to clean up corruption - the retrieval of the moneys stolen by the country’s former ruler was a key campaign message driven home by now president Muhammadu Buhari back in 2015.

It declared: "We are grateful for the international support we're getting in the fight against corruption. Global collaboration is critical to the success of the fight.

“We will continue to work to deepen mechanisms not just for asset recovery but for preventing corruption in the first place."

It is understood the money will be paid back to the African nation in instalments and small amounts.

Roberto Balzaretti, the head of the Swiss delegation to the Global Forum on Asset Recovery (GFAR), told the BBC that if the first instalment is not accounted for by the Nigerian government, further repayments will be halted.

He stated: "It is the first time we are having this sort of trilateral agreement and we feel confident that it will work, plus we signed it in the spirit of trust that the money will be put to good use.”

Nigeria is also chasing a further £358million ($480million) that was allegedly seized in the US.

The UN Office on Drugs and Crime estimates that the African nation lost £298billion ($400billion) to corruption between 1960 and 1999.

Sani Abacha launched a putsch that brought Muhammadu Buhari, the current Nigerian leader, to power in 1983 and another that removed him in 1985.

In 1990 Mr Abacha became the first Nigerian soldier to reach the title of General without skipping a rank.

In 1993 he took the reins of the African nation after overthrowing a transitional government led by Ernest Shonekan before his clear corruption efforts came to light - he is believed to have died after being poisoned by prostitutes sent by his enemies.

After his death, his wife Maryam reportedly attempted to flee the country with 38 suitcases of money.