Mark Thomas is Chief Executive Officer of First Light Fusion, the UK’s only Inertial Fusion Energy company.

First Light is enabling the commercialisation of fusion energy through its unique amplifier technology, which will sit at the heart of the world’s first inertial fusion power plants. This novel technology supports cheaper, simpler and faster pathways to commercial fusion energy.

First Light’s amplifier technology has demonstrated fusion energy across multiple platforms, with results validated by the UK Atomic Energy Authority. The company currently employs 90 leaders, scientists, and engineers in Oxford, UK, and is rapidly evolving into a commercially focused fusion organisation.

Mark joined First Light in 2025 after nearly a decade growing and leading Reaction Engines Limited, a multi-award-winning UK technology company known for its pioneering developments in space propulsion, hypersonic flight, and the delivery of transformational cooling technology solutions for Formula 1 motorsport and zero emissions aviation.

Before joining Reaction Engines, Mark spent 22 years in the Defence and Civil Aerospace divisions of Rolls-Royce plc, most notably in Chief Engineer roles. He worked with customers and industry partners worldwide to lead the design, development and support of new military and commercial aeroengines; Mark’s last role with Rolls-Royce was leading the company’s future civil aerospace programmes and technology demonstrators.

Mark is a Chartered Engineer, Fellow of the Royal Academy of Engineering and the Royal Aeronautical Society. He graduated from Cambridge University in 1993.