Rome, Milan, London: Eni, Royal Dutch Shell and senior executives from both oil companies will face trial over a $1.1 billion (Dh4 billion) bribery scandal in Nigeria, an Italian judge ruled on Wednesday.

The trial will start on March 5 in Milan, judge Giusy Barbara told reporters. The long-awaited decision, initially expected several months ago, will not only affect the two companies but 11 individuals including Eni Chief Executive Officer Claudio Descalzi.

The case is related to the acquisition of a deepwater oil-prospecting license by Eni and Shell in the Gulf of Guinea in 2011. Prosecutors allege that the two companies’ payment of almost $1.1 billion into a Nigerian government escrow account was later distributed as payoffs. While energy producers have come under scrutiny for bribery and corruption in the past, a trial centred around the sitting CEO of an oil major is rare.

“This is really quite a big precedent-setting case,” said Barnaby Pace, a campaigner at watchdog Global Witness, which first shone a light on the alleged transactions. “It’s unusual to see oil majors at the sharp end of the stick in this way,” Pace said by telephone before the decision was announced.

Eni and Shell didn’t immediately comment on the decision. Rome-based Eni previously expressed full confidence in Descalzi and said reviews conducted by external auditors found no illicit conduct. Shell acknowledged in April that it was aware of the destination of part of the payments, but denied wrongdoing.

A final court ruling may take years, bringing steep legal costs for the two companies. The average length of a civil trial in Italy was 460 days in 2016, according to the Ministry of Justice.

Eni and Shell are also facing criminal charges in Nigeria over the same deal. In Europe, Dutch investigators visited Shell’s offices in The Hague in 2016 as part of a probe into the same matter.