Maddy is Chief of Defence Nuclear/2PUS at the Ministry of Defence (MoD) and Additional Accounting Officer for the Defence Nuclear Organisation.

Between December 2020 and September 2022, she was Director General of the Vaccine Taskforce (VTF), a joint unit of BEIS and DHSC, responsible for securing COVID-19 vaccines for the UK, our international donation programme an working with industry to onshore vaccine production. She has made Companion of the Order of Bath for her work on the response to the COVID-19 pandemic.

Before her appointment as Director General in December 2020, Maddy was the lead negotiator for the VTF. Maddy was also the Director for the HRT Task Force for DHSC in 2022. Prior to this Maddy was a Director at UK Government Investments (UKGI) and a non-executive director of UK Export Finance.

Before joining the public sector, Maddy was a Managing Director and Head of UK Mergers and Acquisitions at the investment bank Credit Suisse. She is also a qualified lawyer, having studied law at Trinity College Cambridge and qualifying at Freshfields, working in London, Bangkok and New York.

Maddy was an Honorary Senior Visiting Fellow at the Faculty of Finance at Cass Business School between 2013 and 2016 and holds an honorary doctorate from Nottingham Trent University.