Harrison was born as Adela Lauretta Hutton on 2 January 1913 in Uxbridge, London, as the only daughter of John Percy William Hutton and Ada Lauretta Winn, the latter of whom lived to be 95 years old. She had three brothers, John, George, and Leonard. Her father owned fisheries before entering the fish-and-chips industry.

In 1940, Adela married Frederick A Harrison, and their only child, Paul, was born in 1945. Two years prior, she and her husband moved to Chalfont St. Giles in Buckinghamshire, later moving to nearby Chalfont St. Peter. She worked in the family fish-and-chip shop chain across Middlesex and Buckinghamshire, retiring at the age of 75.

Harrison drove until she was 100, and attended keep-fit classes as a centenarian. On her birthdays, she regularly had sizeable celebrations attended by friends and family all across Europe until her 107th birthday in 2020. As of her 107th birthday, Harrison had five grandchildren and three great-grandchildren. She also claimed that the secret of her longevity was “keeping active, traveling regularly, and eating great fish and chips.”