Diamond McCarthy backs Lansdowne Oil and Gas in $100 million treaty claim against Ireland

AIM-listed Lansdowne Oil and Gas has secured non-recourse litigation funding from US law firm Diamond McCarthy to pursue a $100 million-plus claim against the Irish Government arising from the stalled development of the Barryroe oil and gas field off the coast of Cork.

Under the funding agreement, Diamond McCarthy will fully finance the expected legal costs of the claim, allowing Lansdowne to advance the dispute without further balance sheet exposure. The law firm will act as co-counsel alongside Mantle Law, which has been advising Lansdowne on the matter to date.

The claim is being brought under the Energy Charter Treaty, which provides a framework for investor-state disputes in the energy sector. Lansdowne alleges that Ireland’s refusal in 2023 to grant consent to develop the Barryroe field amounted to a treaty breach, depriving the company of a valuable energy asset in which it holds a 20% interest.

Lansdowne estimates that gross compensation sought will be at least $100 million, plus interest. Under the funding and legal arrangements, the company expects to retain between 60% and 70% of any successful award, with the remainder allocated to legal and funding stakeholders.

The Barryroe field, discovered in 2012 approximately 50 kilometres offshore, is widely regarded as one of Ireland’s most significant undeveloped hydrocarbon prospects. The remaining 80 percent interest is held by Barryroe Transition Energy, formerly Barryroe Offshore Energy, which was recapitalised after entering examinership following the government’s decision.

Lansdowne has said the funding agreement provides the certainty needed to advance the claim to conclusion, while separately pursuing a reverse takeover transaction expected to complete in early 2026.

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