He will become finance director at London’s Moorfields Eye Hospital on 31 August, but will continue working at the Children’s Society part time until 24 September.
Nall will, however, continue to chair the Charity Finance Directors’ Group, because part of his job will be to oversee the finances of the Moorfields Lions Korle Bu Trust, a charity set up by the hospital to reduce blindness in west Africa.
"It’s a very exciting time for the NHS," said Nall. "There’re bags of opportunity as well as bags of things to worry about.
"Moorfields is a very interesting organisation, and a lot of people don’t fully understand what it does," he said. "It’s a super organisation with phenomenal quality and it will allow me to retain my connection with the sector."
Before joining the Children’s Society, Nall was assistant director of the Wolfson Foundation, which awards grant to charities working in areas including science, medicine and health.