Killens has nearly 30 years' experience in the ambulance sector. He is currently Chief Executive of Welsh Ambulance Services University NHS Trust, where he has served for seven years.

His appointment marks a return to London and the ambulance service where he began his career as an emergency medical technician. Killens worked operationally in North East, Central and South East London before taking on leadership roles, including executive director of operations. His time in leadership during his first tenure at London Ambulance included overseeing the 2012 Olympics and responding to the 7/7 London bombing.

He became chief executive of the South Australia Ambulance Service in 2015 before joining the Welsh Ambulance Service as chief executive in 2018.

Killens is the current chair of the Association of Ambulance Chief Executives.

He said: ‘While I'm very excited to take up the London job in my home city, it will be a wrench to leave Wales, which has been such a great privilege to serve.

‘I think it's fair to say that the past seven years have been amongst the most challenging and rewarding of my career, as they have been for so many of us.'