The U.K. attorney general is carrying out a review into why—and how—the Serious Fraud Office (SFO) managed to botch a bribery investigation into Unaoil that saw one of the oil and gas consultancy’s former executives have his conviction overturned.

Suella Braverman announced Wednesday she appointed David Calvert-Smith, a former High Court judge and director of public prosecutions, to investigate the agency’s failings in its case against Ziad Akle, who the Court of Appeal ruled in December had been denied a fair trial.

The court criticized the SFO for its failure to disclose key evidence and “wholly inappropriate” contact with a “fixer” who proposed a backroom deal where key managers would be prosecuted while the company’s owners were left alone.

“We must ensure lessons are learned so that the failings we saw in the Unaoil case can never happen again,” said Braverman in a statement.

The review seeks to determine what went wrong with the SFO’s investigation and procedures and will provide recommendations about how to ensure similar mistakes are not made again.

It will assess the details surrounding the SFO’s contact with third parties and why the agency failed to disclose vital evidence that ultimately prejudiced the trial.

The review will also examine the implications the failings might have for the policies, practices, procedures, and related culture of the SFO and what changes might need to be made.

Presently, there is no indication a key change might be replacing SFO Director Lisa Osofsky, whose term runs out next year.

Also Wednesday, Osofsky was grilled by Members of Parliament about the SFO’s track record under her watch, particularly regarding the quashed Unaoil conviction and collapse of the agency’s eight-year investigation into two former Serco executives because of disclosure failures.

The attorney general’s review should be concluded before the end of May. An SFO spokesperson said the agency was fully cooperating.