The Ontario court paves the way for a class action lawsuit against Endeavour Mining Plc following revelations related to the management of its former CEO, Sébastien de Montessus. In a decision rendered on August 31, 2026, the Ontario Superior Court of Justice granted the plaintiff investors permission to pursue their action under the Ontario Securities Act and certified the case as a class action.
The case pits two investors, Alan Newsome and Carson Wong, against Endeavour Mining Plc, Endeavour Mining Corporation, as well as several former executives and directors, including Sébastien de Montessus, Guy Young, Joanna Pearson, and members of the audit committee.
At the heart of the case are allegations that the former CEO bypassed internal control mechanisms and misled the board of directors on several financial transactions. The Court notes that the plaintiffs’ action follows the termination of Sébastien de Montessus’ contract in January 2024, after Endeavour revealed an irregular payment instruction of 5.9 million US dollars related to the sale of the Agbaou mine in Côte d’Ivoire to Allied Gold Corporation.
According to the court decision, Endeavour then announced the results of an external investigation on March 27, 2024, revealing that the former executive had “overstepped” certain financial controls, moved more than 20 million dollars out of the company’s usual channels, falsified some documents, and provided inaccurate information to the board, the audit committee, and investigators.
The lawsuit focuses on four main categories of allegations: corporate governance, internal financial controls, commitments to workplace environment and professional conduct, as well as compliance with IFRS accounting standards.
A CAD 625 million stock market drop after the announcement
The announcement of Sébastien de Montessus’ departure on January 4, 2024, triggered an immediate market reaction. Endeavour Mining’s stock price dropped from 28.48 dollars to 25.98 dollars on the same day, while the market capitalization reportedly decreased by around 625 million Canadian dollars within ten minutes of the announcement, according to evidence reviewed by the Court.
The company had indicated that it had dismissed its CEO “for gross misconduct with immediate effect,” citing an irregular payment instruction of 5.9 million dollars and allegations of inappropriate personal behavior under external investigation.
Payments of 15 million dollars to an entity in the UAE
The extended investigation conducted after the executive’s departure also focused on two payments made in 2020 totaling 15 million dollars to an entity based in the United Arab Emirates, which had also received the payment related to the Agbaou operation.
The Court reports that investigators concluded that Sébastien de Montessus had presented documents describing this entity as related to a service provider, while the identity of the ultimate beneficiary could not be established in the internal investigation.
Endeavour: “a former CEO who circumvented controls”
In its public documents, Endeavour described the facts as a “deliberate circumvention of controls, active concealment, and inaccurate statements” by its former executive. The company announced several corrective measures, including strengthening controls at two levels for certain M&A operations and improving internal alert procedures.
The company also initiated a clawback of payments made to Sébastien de Montessus for an announced amount of 29.1 million US dollars.
The Ontario court decision does not constitute a final judgment on the liability of the parties involved. However, it allows the plaintiffs to continue their action and opens the way for a thorough examination of the governance and internal control practices of the mining group listed in London and Toronto.
Endeavour Mining, one of the leading gold producers in West Africa, thus enters a new legal phase whose stakes go beyond the former executive alone: that of the responsibility of monitoring mechanisms in an international mining company.
