Publication of Independent Resource Evaluation

3 June 2025

Rockhopper Exploration plc

("Rockhopper" or the "Company")

Publication of Independent Resource Evaluation

Rockhopper Exploration plc (AIM: RKH), the oil and gas company with key interests in the North Falkland Basin ("NFB"), is pleased to announce the publication of an independent resource evaluation conducted by Netherland, Sewell & Associates, Inc. ("NSAI") on behalf of Rockhopper.

Key information:

- Unrisked gross contingent resources 2C 917 mmbbls

o  321 mmbbls net to Rockhopper

- Unrisked gross contingent resources development pending 2C 727 mmbbls

o  255 mmbbls net to Rockhopper

- Value of the Rockhopper net 2C 255mmbbls 35% working interest in Sea Lion is US$1.8bn

o  net of royalties and taxes at an oil price of US$70 Brent

Rockhopper holds a 35% working interest in Sea Lion and associated NFB licences and benefits from various loans from Navitas Petroleum ("Navitas") in relation to the development, which have been detailed in previous announcements.

Highlights of NSAI independent resource evaluation (oil only):

\* Totals may not sum precisely due to rounding adjustments

\* Totals may not sum precisely due to rounding adjustments

The development scenario assumed in the report underlying the NPV calculation aligns with the previously disclosed multi-phase 2 FPSO scheme comprising the Northern Development Area phases 1, 2 & 3 along with the Central Development Area phases 1 & 2.

Navitas continues to estimate Capex to first oil on phase 1 of cUS$1.4 bn and in this regard has entered into a number of agreements including an MOU for a FPSO which is currently operating in UK offshore waters, along with various contracts for critical path long lead items including provision of subsea equipment and flexible flowlines.

Additional notes

In a change to previous naming conventions, the entirety of the oil deposits in licences PL032 and PL004 are now referred to as Sea Lion. Previously, Rockhopper had referred to Sea Lion separately from the Isobel / Elaine accumulation; that is no longer the case.

The difference of 3 mmbbls between the 2C development pending 727 mmbbls contained in the Rockhopper NSAI report and the 2C development pending 730 mmbbls in the Navitas NSAI report is a result of running the reports at different oil price decks resulting in a small change to the economic cut off for the field. All of the underlying data and other assumptions are consistent.

NSAI have also provided estimates of gross and working interest of i) Contingent Gas Resources, and ii) Prospective Oil and Gas Resources however the Company has not reproduced them in this summary as there is no plan for their development in place. NSAI's report also includes economic analysis with a low and high oil price sensitivity.

A full copy of the report will be available later today on the Rockhopper's website: https://rockhopperexploration.co.uk/

Sam Moody, Chief Executive Officer of Rockhopper, commented:

"We are delighted that NSAI have been able to confirm the best estimate potential value of Rockhopper's 35% working interest in Sea Lion is US$1.8bn net of taxes at an oil price of US$70. 

"We continue to work with the Operator to unlock this potential value for all stakeholders."

Enquiries:

Rockhopper Exploration plcSam Moody - Chief Executive OfficerTel. +44 (0)20 7390 0230 (via Vigo Consulting)

Canaccord Genuity Limited (NOMAD and Joint Broker)Henry Fitzgerald-O'Connor/James Asensio/Charlie HammondTel. +44 (0) 20 7523 8000

Peel Hunt LLP (Joint Broker)Richard Crichton/Georgia Langoulant

Vigo ConsultingPatrick d'Ancona/Ben Simons/Fiona HetheringtonTel. +44 (0) 20 7390 0234

Resource Disclosure

The NSAI Independent Resource Evaluation has been produced to PRMS standards. approved by the Society of Petroleum Engineers ("SPE").

Lucy Williams (BSc Geology, MSc Petroleum Geology, Chartered Geologist) the Company's Geoscience Manager has reviewed and approved the technical information contained within this announcement.