David joined St. John New Zealand in 1997 and since then has volunteered and worked as an event volunteer, first aid instructor, volunteer ambulance officer, paramedic and finally senior clinical tutor. He has also been involved with St. John Ambulance Australia in both New South Wales and Victoria as a Senior Medical Officer.  He was admitted to The Order of St. John as a Member in 2007. 

Professionally, he is the Medical Director of Ambulance Victoria – one of the largest and busiest ambulance services in the world, covering all of Victoria, Australia; he is also an intensive care physician at The Alfred Hospital, Melbourne – a quaternary referral centre for heart and lung transplant, ECMO, major trauma and burns; and an Adjunct Associate Professor in the Department of Paramedicine at Monash University. 

While volunteering and working with St. John, David completed an undergraduate science degree followed by medical training at the University of Auckland before undertaking postgraduate training in intensive care medicine. During postgraduate training he spent considerable spells working in anaesthesia, palliative medicine and prehospital and retrieval medicine in Auckland, Sydney and Toronto before settling in Melbourne. His clinical interests are prehospital and retrieval medicine, trauma critical care, resuscitation, palliative care and bioethics.