A witness of truth, vindicated at every level.

The Commission formed a favourable view of his evidence.

In the corruption inquiry that exposed the Mount Penny coal scandal, the Independent Commission Against Corruption relied on Mr Brook's evidence and assessed it directly in its report to Parliament.

The Commission formed a favourable view of Mr Brook and his evidence; he gave his evidence in a slow and careful way, and in a manner that was designed to be generally honest and accurate. There were numerous instances where Mr Brook gave evidence that was against his own self-interest.Commissioner the Hon. David Ipp AO QC — ICAC Operation Jasper report, July 2013

Where his account conflicted with that of the Obeids, the Commission generally preferred Mr Brook's evidence. It did not recommend that consideration be given to his prosecution for any offence.

The Federal Court found his evidence “essentially reliable.”

In the competition proceedings brought by the ACCC against the Cascade Coal directors, the Court weighed Mr Brook's testimony against the documentary record and against the accounts of opposing parties.

For the most part, his evidence was entirely consistent with the documentary record … Overall, I consider that his evidence was essentially reliable.Foster J — ACCC v Cascade Coal Pty Ltd (No 3) [2018] FCA 1019

The Court preferred Mr Brook's evidence over that of the opposing directors — a second, independent judicial validation of his account.

Vetted and cleared by the corporate regulator.

Mr Brook was formally vetted and cleared by the Australian Securities and Investments Commission as an Authorised Representative (No. 001282075, 2020–21) — an appointment that requires meeting the regulator's “Fit and Proper” person standard.

The people he testified against were convicted — and jailed.

Following the judge-alone trial, Justice Fullerton convicted Edward Obeid, Moses Obeid and Ian Macdonald of conspiracy to commit misconduct in public office and, on 21 October 2021, sentenced each to prison. In assessing the gravity of the corruption, her Honour found:

I am satisfied, for that complex of reasons, the objective seriousness of the conspiracy was of the highest order.Fullerton J — R v Macdonald; R v Edward Obeid; R v Moses Obeid (No 18) [2021] NSWSC 1343; (2021) 394 ALR 125; (2021) 292 A Crim R 506

Ian Macdonald was sentenced to 9 years and 6 months' imprisonment (non-parole period 5 years 3 months); Edward Obeid to 7 years (non-parole 3 years 10 months); and Moses Obeid to 5 years (non-parole 3 years).

National broadcast — and the broadcaster's own clarification of his good faith.

In November 2021 the ABC's flagship investigative program Four Corners examined the Obeid family's dealings in the episode “Obeid Inc.”, reported by Angus Grigg under Executive Producer Sally Neighbour. Mr Brook was interviewed as a key witness. The ABC subsequently published an editor's note clarifying the nature of his cooperation:

The highest court in the land — the final word.

The men Mr Brook testified against were convicted in the NSW Supreme Court in 2021; their appeals were dismissed by the Court of Criminal Appeal and, on 4 February 2026, unanimously dismissed by a full seven-member bench of the High Court of Australia — permanently upholding their convictions for conspiracy to commit misconduct in public office, and exhausting the appellate chain at every level.

The corruption Mr Brook helped expose is now a matter of settled law, affirmed by the nation's highest court. The account the courts preferred has been vindicated in full.