Bloemfontein - The radical views of a man implicated in the alleged 2012 Mangaung terror attack drew police's attention to the plot, the Bloemfontein High Court heard on Tuesday.
Judge MH Rampai was listening to evidence in the treason and conspiracy trial of Johan Prinsloo, 50.
Prinsloo faces charges of treason, conspiracy to take part in terrorist acts and possession of illegal ammunition.
Prinsloo, Mark Trollip, 48, and Martin Keevy, 49, were arrested in connection with an alleged plan to attack the African National Congress's Mangaung conference in December 2012.
“We decided to look at Keevy, who was more radical than GVR (Geloftevolk Republikeine),” the police agent told Rampai.
“What he wanted was anarchy.”
The State submitted that President Jacob Zuma and Cabinet ministers were the main targets.
On Tuesday, the infiltrator, who can not be identified because of a provisional court order, was being cross-examined by Prinsloo's legal counsel, Johann Nel.
Nel mostly tested the man's testimony in chief about his original orders to infiltrate the right-wing group, Covenant People Republicans (Geloftevolk Republikeine).
Mr A, as the State called him, testified it was during his work on the Covenant People Republicans that he met Keevy at a meeting at the Bloemfontein CVO school.
Replying to a question, Mr A submitted that Keevy did not seem to be part of a organised group, but acting as an individual.
The agent said he met the other Mangaung conspirator, Mark Trollip, at a meeting in Kroonstad, where the Bloemfontein attack was mentioned for the first time.
Trollip has already pleaded guilty to a charge of conspiracy and was sentenced to eight years in prison last year.
At the meeting, Trollip said he already had people and weapons for such an attack on the ANC's conference at the grounds of the University of the Free State.
Keevy was declared unfit for trial in October, and was declared a patient of the State.
The State alleges that Prinsloo, Keevy and Trollip illegally tried to overthrow the South African government by trying to get weapons and ammunition to attack the country's leaders on December 16, 2012.
Prinsloo apparently also tried to help the Boerevolk to govern through an unconstitutional way.
Earlier, the police infiltrator testified that he met Prinsloo in Ficksburg only weeks before the planned attack.
It was at a time when the plotters were apparently trying to get weapons from Lesotho.
The trial continues.