Wednesday 6 May 2026

United Kingdom National Nuclear Laboratory (UKNNL) has announced the appointment of Brian Tenner as Chief Financial Officer (CFO) and Mandy Clarke as a Non-Executive Director, further strengthening UKNNL’s leadership as the organisation continues to deliver on its mission.

The appointments reflect a deliberate and purposeful approach to building the right leadership for UKNNL’s next chapter, bringing together financial expertise, governance experience and a deep commitment to the values that will carry the organisation forward.

Brian Tenner appointed Chief Financial Officer

Brian Tenner joins UKNNL with over 30 years of finance, strategy and operational leadership experience across the energy, nuclear and technology sectors. He brings a strong track record of delivering major financial and operational transformation programmes in complex, regulated organisations, having previously served as Finance Director for British Nuclear Group and chaired the Audit Committee at AWE.

His expertise in financial control, governance and stakeholder value, combined with direct experience of the nuclear sector, means he is well-placed to support UKNNL through its next phase.

Brian said: “UKNNL is an organisation with a genuinely important mission, and I’m delighted to be joining at such a significant moment in its journey. My focus will be on building the financial foundations that give UKNNL the stability and confidence to look forward, and supporting the organisation to deliver for its customers, its people and the wider nuclear sector. I’m looking forward to getting to know colleagues and getting to work.”

Mandy Clarke appointed Non-Executive Director

Mandy Clarke joins the UKNNL Board as a Non-Executive Director as part of the natural cycle of board renewal. Following a career as a commissioned officer in the Royal Air Force, she brings over 25 years of executive-level experience in people strategy, organisational development and transformation, alongside more than 15 years as a non-executive board member across a range of organisations.

She currently serves as a Non-Executive Director at The Pensions Regulator, where she chairs the Remuneration and People Committee, and as a board member at Platform Housing Group. She is also the independent chair and trustee of Engage Technical Solutions.

Mandy said: “I am very pleased to be joining the UKNNL Board at such an important time for the organisation and for the wider nuclear sector. I hope to bring the benefit of my experience in people, culture and governance to support UKNNL as it continues its transformation. Strong organisations are built on the back of clear values, the right culture and the right leadership. I look forward to playing my part in that.”

UKNNL CEO Julianne Antrobus said:

“Brian and Mandy join us at an important moment, and I’m delighted to welcome them both to UKNNL. These planned appointments are the result of thoughtful recruitment and board renewal processes, and they reflect our commitment to putting the right leadership in place as we move forward with purpose.

“Brian’s deep experience in financial transformation and his familiarity with the nuclear sector will be invaluable as we continue to build the strong financial foundations UKNNL needs. And Mandy brings a breadth of governance, people and organisational expertise that will strengthen our board. Importantly, both Brian and Mandy embody the values we expect of our leaders at UKNNL, and I know they will be a brilliant addition to the organisation.

“I also want to take this opportunity to say a sincere thank you to Val Brown, whose contribution as Interim CFO over the past eight months has been quite exceptional. Val led with skill and quiet determination, and UKNNL is a stronger organisation for it. I’m delighted she continues with us in her role as VP Finance. I would also like to thank Ann Cormack, whose support, counsel and enthusiasm on UKNNL’s Board have been greatly valued. Ann has been a real asset to UKNNL and we wish her well.

“Together, these appointments send a clear signal: UKNNL is building the leadership and the foundations it needs to deliver on its mission for decades to come.”