The information contained within this announcement is deemed by the Company to constitute inside information as stipulated under the retained EU law version of the Market Abuse Regulations (EU) No. 596/2014 . Upon the publication of this announcement via Regulatory Information Service, this inside information is now considered to be in the public domain. If you have any queries on this, then please contact Steve Boldy, the Chief Executive Officer of the Company (responsible for arranging release of this announcement).

11 May 2026

Lansdowne Oil & Gas plc

("Lansdowne" or the "Company")

 Update on Energy Charter Treaty ("ECT") Arbitration Claim

Lansdowne Oil & Gas is pleased to announce that, following the filing of a Request For Arbitration ("RFA") regarding its dispute with Ireland regarding the Barryroe oil and gas field, at the International Centre for Settlement of Investment Disputes ("ICSID") in Washington, D.C., on the 8 May 2026 the Company received written confirmation from ICSID that the ICSID Secretary-General has registered the Request. Details of the Arbitration can be found on the ICSID Website.

This is an important step in the arbitration process and will now be followed by the appointment of a tribunal. Lansdowne will continue to vigorously assert its rights under the Energy Charter Treaty ("ECT") in its dispute with Ireland. As previously reported, the Company is pursuing a claim of a minimum US$100 million plus interest.

On 27 April 2026 the ECT Secretariat announced that it had received notification of Ireland's withdrawal from the Treaty. It further noted that this will become effective one year after its notification to the Secretariat - from 28 April 2027. It also noted that Ireland will continue to be bound by the 20-year sunset clause. Accordingly, Ireland's withdrawal from the ECT will have no bearing on Lansdowne's case.

In June 2023 Lansdowne gave notice to Ireland that a dispute existed under the ECT and the filing and registration of the RFA brings to a close the first formal step in the arbitration process.

Stephen Boldy, CEO of Lansdowne commented:

"On behalf of Lansdowne and all our shareholders, I would like to thank the legal teams from Diamond McCarthy and Mantle Law who have worked to produce the RFA and we look forward to the next steps in the arbitration process in our quest to seek just compensation for the loss of our Barryroe asset."

"It is expected that the Company will recommence trading on the AIM of the London Stock Exchange on 27 May 2026, subject to shareholder approval of the resolutions at the upcoming General Meeting on 26 May 2026."

For further information please contact:

Notes to editors:

About Lansdowne

Lansdowne Oil & Gas (LOGP.LN) is an oil and gas exploration and appraisal company quoted on the AIM market that was previously focused on the North Celtic Sea.

In May 2023 the application for a Lease Undertaking for the Barryroe oil and gas field, in which Lansdowne held a 20% interest, was refused by the Irish Department of the Environment, Climate and Communications.

In June 2023 Lansdowne announced the commencement of action under the Arbitration Process of the Energy Charter Treaty.

On 20 September 2023 Lansdowne announced that, under AIM Rule 15, the Company had been designated to be a cash shell. Accordingly, the shares of the Company were suspended from trading on AIM as at 07.30am on 21 March 2024.  

On 30 April 2026, Lansdowne announced the completion of a Reverse Take Over to acquire Sao Gabriel Mining, who hold graphite assets in Brazil, accompanied by a placing to raise £1.9 million before costs. This transaction is subject to shareholder approval at the forthcoming AGM on 26 May 2026.

For more information on Lansdowne, please refer to www.lansdowneoilandgas.com.