Rockhopper Regulatory News (RKH)

Embargoed: 0700hrs, 4 April 2011

Rockhopper Exploration plc

(the "Company")

14/10-4 Appraisal well - further technical update

Rockhopper Exploration plc (AIM: RKH), the North Falkland Basin oil and gas exploration company, is pleased to provide the following technical update on its Sea Lion Discovery after further interpretation of the results of well 14/10-4:

·; Porosity in 14/10-4 in the range 15%-27%, average 20%

·; Net to gross within the pay zone of 88%

·; Dual packer modular formation dynamic tester (MDT) results indicated well had the potential to flow at 2,700 bbls per day, compared to c.2,000 bbls per day seen in 14/10-2

·; Management interprets new low case area of 22km2 with stock tank oil initially in place (STOIIP) of 516 mmbbls giving 155 mmbbls recoverable at 30% recovery factor

·; New seismic depth conversion confirms upper fan full to spill, oil water contact within the upper fan package at 2,477m true vertical depth subsea (TVDSS)

·; Analysis of MDT results and logging indicates 14/10-2 and 14/10-4 are in communication.

A presentation containing this information is available on the Company's web site: www.rockhopperexploration.co.uk

Enquiries:

Rockhopper Exploration plc

Sam Moody - Chief Executive

Tel. +44 (0)20 7920 2340 (via M: Communications)

M: Communications

Patrick d'Ancona or Ben Simons

Tel. +44 (0)20 7920 2340

Canaccord Genuity Limited

Charles Berkeley / Henry Fitzgerald-O'Connor

Tel. +44 (0) 20 7050 6500

Notes to Editors

Rockhopper was established in February 2004 with a strategy to invest in and carry out an offshore oil exploration programme to the north of the Falkland Islands. The Company floated on AIM in August 2005 and holds a 100 per cent. interest in four offshore production licences: PL023, PL024, PL032 and PL033 which cover approximately 3,800 sq. km. Rockhopper has also farmed in (7.5% working interest) to licences PL003 and PL004, which are operated by Desire Petroleum. These licences have been granted by the Falkland Islands government.

An extensive work programme has been carried out over a number of years on the licences operated by Rockhopper. This has included 2D and 3D Seismic and Controlled Source Electromagnetic Mapping (CSEM). In February 2010, the Ocean Guardian drilling rig arrived in Falkland waters to carry out a multi-well drilling campaign. Rockhopper drilled an exploration well on its Sea Lion prospect during April and May 2010, the result of which was the first oil discovery and Contingent Oil Resource in the North Falkland Basin. The Sea Lion discovery was successfully tested during September 2010 and was the first oil to flow to surface in Falkland Islands waters. Rockhopper contracted seismic vessels MV Polarcus Asima and Nadia to carry out 3D seismic surveys, beginning December 2010, over areas of licences PL024, PL032 and PL033 which were not previously defined by 3D, as well as adjacent areas.

Rockhopper Exploration plc www.rockhopperexploration.co.uk

NB: This statement has been approved by the Company's geological staff who include David Bodecott (Exploration Director), who is a Member of Petroleum Exploration Society of Great Britain (PESGB) and the American Association of Petroleum Geologists (AAPG) with over 30 years of experience in petroleum exploration and management, for the purpose of the Guidance Note for Mining, Oil and Gas Companies issued by the London Stock Exchange in respect of AIM companies, which outline standards of disclosure for mineral projects.