Public Protector Busisiwe Mkhwebane has been the target of a public outcry over the past few months, with questions being raised about her fitness to hold office.

Now, her predecessor, Thuli Madonsela, has raised questions about why Mkhwebane closed her investigation into the justice, crime prevention, and security (JCPS) cluster probe into the Gupta Waterkloof landing in 2013.

In an article published in Business Day on Tuesday, the newspaper quoted Madonsela as saying: "The truth is the investigation was completed and all we needed was a report. How after that they closed the investigation is a mystery."

Western Cape Finance MEC David Maynier of the DA originally laid the complaint with the Public Protector in 2013 and says he does not support Mkhwebane's decision.

"I don't think the truth of the incident has ever been made public and I think it should. Nobody was ever really held accountable for what happened, in fact the reverse happened, everybody who was involved in that incident, which was a national scandal, was promoted," Maynier said.

He continued: "A third issue that needs to be looked at is the practice of closing investigations but keeping the fact of that secret. There is now a question of other investigations that have been closed and not been made public."

Maynier's complaint related to the Gupta family landing a private aircraft at Waterkloof Air Force Base carrying 270 guests who were attending a wedding at Sun City. The landing caused a stir among the public and, in a symbolic way, was said to be the beginning of the public's exposure to the inner workings of state capture. The Public Protector's investigation related to Lieutenant Colonel Christine Anderson who was implicated as the responsible person in the JCPS cluster probe.

Anderson subsequently complained that the probe was "irregular". She was then charged with contravening the military defence code, but these charges were later dropped. As a result, Mkhwebane seemed to believe that her investigation would be null and void.

The JCPS investigation

The JCPS cluster exonerated then-president Jacob Zuma and his ministers but implicated, among others, two people – Bruce Koloane, the ambassador to the Netherlands, as well as Anderson. The report said they had irregularly given clearance for the landing.

"The activities of Ambassador Koloane and Lieutenant Colonel Anderson were a serious dereliction of duty in that they were advancing the objectives of this project to the detriment of their official responsibilities."

It continues: "Their activities also indicate the bringing to bear of undue influence on state officials, systems, equipment and infrastructure … the roles of the two individuals had a similar effect in that due to their seniority and knowledge of departmental systems and processes in their respective areas, they both grossly abused and undermined these processes."

The two, along with other co-accused, appeared in the military court at the Thaba Tshwane military base in Pretoria in 2013 and were charged with contravention of the military defence code.

Feeling that the probe "irregular", Anderson then took to the Public Protector, saying she was used as a scapegoat. Maynier also went to the Public Protector, asking Madonsela to investigate the role of Cabinet members and events leading up to the Waterkloof landing.

Madonsela rejected this complaint due to insufficient evidence to justify it. In a letter to Maynier, Madonsela said she would, however, investigate the task team.

"We will pursue this matter in respect of the complaint lodged by Col. Anderson where she had expressed dissatisfaction in the matter in which the task team dealt with the investigation in so far as her participation in the process was concerned."

She alleges that the task team conducted itself in an irregular manner by making findings against her without having given her an opportunity to respond before the report was published similarly."

Maynier welcomed this response.

"We have maintained from the start that the JCPS task team's investigation was a carefully crafted damage control exercise designed to protect President Zuma and members of his Cabinet from the political fallout generated by 'Guptagate'."

The investigation seemed to ruffle some feathers and in 2015 charges were withdrawn against Anderson. Koloane, on the other hand, became the fall guy and pleaded guilty to all charges. This withdrawal seems to be the basis upon which Mkhwebane has closed the case because an investigation would at that point be worthless.

Madonsela, in reply, told Business Day: "The report was important because it pointed to security fault lines beyond Anderson's case. We interviewed everyone, including task team members [including then-correctional services commissioner Tom Moyane] and got the radio record."

Mkhwebane has recently been under fire for three of her reports being set aside by the courts and has subsequently been labelled as Zuma's last line of defence.