Paul Remington vice chair of the East of England Ambulance trust thanks Ms Ball for her hard work.
He said: “Maria spent many years leading the ambulance service and I would like to thank her for her dedication and commitment through what have been some challenging times.
"Maria oversaw the formation of this Trust, bringing together three disparate organisations into one service, and its subsequent development."
More top news
Photographs of one of Britain's largest medieval cemeteries have been released to the public for the first time.
A multi-million pound campaign to relaunch Britain's Airship industry in the Bedfordshire countryside has begun.
Cloud and rain will spread eastwards throughout tonight.