He studied history at Corpus Christi College, Cambridge, achieving a double first, and received an MBA from the Stanford Graduate School of Business, which he attended on a Harkness Fellowship.

Between 2000 and 2002 he chaired the board of video games retailer Gamestation through a period of growth that took it from 26 to 70 outlets and negotiated its sale to Blockbuster.

[6] In 2011 he was appointed strategy advisor at HRV Fit, developer of ithlete, the mobile heart rate variability application.

[14] Following the establishment by the Government of Jersey of an Advisory Board for the Crown Dependency's Health and Community Services in 2023, Hayhoe was appointed as its first permanent chair[15] but departed after little more than a month citing differences in working style with the Jersey government minister, Deputy Tom Binet[16][17] only days after announcing plans to spend taxpayers' money efficiently, make the system more transparent and improve the board's engagement with the public.

[18][19] Hayhoe has worked extensively in regulatory roles alongside his other appointments, serving as an Executive Reviewer for the Care Quality Commission and an external assessor for the College of Policing and chairing Fitness to Practise Panels for the Nursing and Midwifery Council and Disciplinary Committee hearings for the Association of Chartered Certified Accountants.

[21][22] In December that year he was appointed Covid Counter-Fraud Commissioner in HM Treasury on a one-year contract to examine an estimated £7.6 billion of Covid-related fraud with a remit stretching beyond disputed PPE contracts to include spuriously received business support loans and grants; erroneously claimed furlough payments; and abuse of the Eat Out to Help Out scheme.