Change of Substantial Shareholder

3 September 2026 - Singapore: Jadestone Energy plc (AIM:JSE) (the "Company" and together with its subsidiaries, "Jadestone" or the "Group"), an independent upstream production and development company focused on the Asia-Pacific region, announces that it has been formally notified by PT Prima Petroleum Energi ("Prima Energy") that Prima Energy has acquired 154,094,444 ordinary shares of £0.001 par value in the Company (the "Sale Shares"), representing approximately 28.3% of the Company's issued share capital (the "Sale").

The Sale Shares were held by Tyrus Capital Special Situations Master Fund Sarl, SICAV-RAIF, TC Six Limited and TC Special Private Equity Opportunities IV Limited. Following completion of the Sale, funds managed by Tyrus Capital S.A.M. ("Tyrus") hold no ordinary shares in the Company, and Prima Energy holds 154,094,444 ordinary shares, representing approximately 28.3 per cent. of the Company's issued share capital.

The Sale was bilaterally arranged between Tyrus and Prima Energy. The Company received no proceeds from the Sale. There is no change to the Company's issued share capital, with 544,936,979 shares currently in issue.

Dr. Adel Chaouch, Executive Chairman of Jadestone, commented:

"Tyrus was a significant shareholder in Jadestone for over a decade, and the Company would not have established itself as a leading independent in the Asia-Pacific region without Tyrus' support and engagement. We thank the Tyrus team and wish them well in the future.

We are pleased to see the sale of Tyrus' holding completed at what we understand to be a very substantial premium to the average share price over the last month. It is a clear endorsement of the value in our Asia-Pacific platform and assets by a notable regional strategic investor, and we look forward to engaging constructively with Prima Energy to deliver on our strategic objectives.

Since I joined Jadestone and with the efforts of a refreshed and revitalised management team, we have deepened and strengthened our relationships with the national oil companies, regulators and contractors in our core jurisdictions in Asia-Pacific. The significant progress we have made this year on commercialising our Vietnam gas discoveries is clear evidence of strategic delivery for our shareholders. We look forward to redoubling those efforts to deliver further value and benefits for all stakeholders over the coming months and years."

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About Jadestone Energy

Jadestone Energy plc is an independent upstream company focused on the Asia-Pacific region. It has a balanced and increasingly diversified portfolio of production and development assets in Australia, Malaysia, Indonesia and Vietnam, all stable jurisdictions with a positive upstream investment climate.

The Company is pursuing a strategy to grow and diversify the Company's production base both organically, through developments such as Nam Du/U Minh in Vietnam and the Puteri Cluster offshore Malaysia, as well as through acquisitions that fit within Jadestone's financial framework and play to the Company's strengths in regional upstream development and operations and managing maturing oil assets. Jadestone delivers value in its acquisition strategy by enhancing returns through operating efficiencies, cost reductions and increased production through further investment.

Jadestone is a responsible operator and well positioned for the energy transition through its increasing gas production, by maximising recovery from existing brownfield developments and through its Net Zero pledge on Scope 1 & 2 GHG emissions from operated assets by 2040. This strategy is aligned with the IEA Net Zero by 2050 scenario, which stresses the necessity of continued investment in existing upstream assets to avoid an energy crisis and meet demand for oil and gas through the energy transition.

Jadestone Energy plc (LEI: 21380076GWJ8XDYKVQ37) is listed on the AIM market of the London Stock Exchange (AIM: JSE).  The Company is headquartered in Singapore.  For further information on the Company please visit www.jadestone-energy.com.

PT Prima Petroleum Energi is an Indonesian company and part of the Prima Energi Group based in Jakarta, Indonesia, which operates in the oil and gas industry, both in upstream production and as a service provider.  More information can be found at https://www.primaenergy.id/.

The information contained within this announcement is considered to be inside information prior to its release, as defined in Article 7 of the Market Abuse Regulation No. 596/2014 which is part of UK law by virtue of the European Union (Withdrawal) Act 2018.