On this page you can meet the ESO’s Executive Team.

Led by the Executive Director, the ESO Executive Team has overall responsibility for the ESO and the delivery of a safe, efficient and reliable electricity network.

Fintan Slye National Grid ESO

Fintan Slye, Executive Director

Fintan joined National Grid ESO in 2018. Prior to that he was Chief Executive of the EirGrid Group, the electricity system and market operator in Ireland and Northern Ireland.  He previously also worked for McKinsey (2006-2008) in Ireland and UK and ESB (1994 – 2006) in Ireland, Europe and the US. 

Fintan holds Master’s degrees in engineering and Business Administration along with diplomas in legal studies and European Law.

Isabelle Haigh, National Grid ESO

Isabelle Haigh, Head of National Control

Isabelle joined ESO in March 2021 from Gas Transmission where she was heading up the operational field force. She graduated in Electrical and Electronic Engineering and has had 30 years working in the industry for National Grid. Previous roles have included; being the first female engineer in the Birmingham Grid Centre, designing voltage management schemes, designing and managing balancing services and leading large transformation projects such as the development of the Transmission Network Control Centre, and a fixing the basics programme in Gas Transmission.

Julian Leslie, Head of Networks and ESO Chief Engineer

Julian has had almost 30 years’ experience in electricity system operation for National Grid. This included 4 years working in National Grid US developing a new system operator function for a large part of the Mid-West of America. Julian has a degree in Electrical Engineering, is a Chartered Electrical Engineer and a Fellow Member of the Institute of Engineering and Technology.

Kayte oNeil

Kayte O’Neill, Head of Markets

Kayte joined ESO in 2018 and prior to her current role as Head of Markets led the Strategy and Regulation team where she was accountable for delivering the RIIO2 price control. She has held a wide variety of senior roles across the business, including three years in Boston with National Grid’s US electricity distribution businesses. Kayte holds a first-class degree in Business Economics and is a graduate of the Harvard Business School Program for Leadership Development. She is a Director on the ESO Board and a Non-executive Director on the Regen Board.

Matthew Wright

Matthew Wright, Head of Strategy and Regulation

Matthew has over 30 years of experience in the utilities sector, most recently as Managing Director of Ørsted in the UK. He has also served as CEO of Southern Water and EVP of Power Delivery at US electric utility PacifiCorp. He is a Board member of POWERful Women, a professional initiative to advance gender diversity within the energy sector.

Huma Ali

Huma Ali, Head of HR

Huma joined the ESO in 2015 having previously worked in a variety of HR roles across National Grid Group and its predecessors. She holds a degree in Business Management and is Chartered status with the Institute of Personnel and Development.

Gregg Smith

Gregg Smith, ESO CFO

Gregg joined National Grid ESO in 2020 after 21 years with IMI plc. Gregg holds a degree in Business Economics and is a qualified Chartered Management Accountant (ACMA and CGMA). Gregg held several global roles across all three IMI divisions throughout his career and has worked in the US, Spain and Switzerland.

Jake Rigg Profile

Jake Rigg, Head of Corporate Affairs

Jake is Director of Corporate Affairs at National Grid Electricity System Operator (ESO). Jake joined the ESO from Affinity Water, the water supplier to 3.7 million people in the South-East. At Affinity he led on environmental sustainability and innovation work as Corporate Affairs Director, in particular championing chalk streams. He has also worked on sustainability issues as a consultant to several large companies including investment banks and clearing houses, DuPont, and 3M. He was an advisor to a former Secretary of State for Energy and Climate Change. He has a degree in modern history from Oxford and is currently completing research on quantifying political and regulatory risk at Yale. He lives in Buckinghamshire with his wife and two daughters.


Zoe Morrisey

Zoe Morrisey, ESO Legal Counsel and Company Secretary

Zoe joined National Grid in 2012 and has worked across the various UK business units advising on a range of regulatory and commercial matters. Prior to joining National Grid Zoe worked for Ofwat and in private practice in the competition and procurement team having qualified to practice as a solicitor in 2008. Zoe has a degree in Law with German as well as two postgraduate diplomas in competition law and economics for competition law.