Dorothea Nancy Waddingham was born Dorothy Nancie Merelina Allan Chandler on June 21, 1899. She was born on a farm near Nottingham, England. Her parents married a year after her birth. Waddingham was named after her father's surname. As a child, she grew up in a rural area, but details about her early childhood are not widely known.

Dorothea did not have formal training as a nurse. The only medical experience she had was working as a ward-maid at an infirmary near Burton-on-Trent. This limited training contributed to her later reputation as "Nurse" Waddingham.

In 1925, Dorothea married Thomas Willoughby Leech. He was significantly older than her, almost twice her age, and was suffering from cancer. During their marriage, she faced legal troubles and served two prison sentences for fraud and theft. Dorothea and Thomas had three children together. Sadly, Thomas died in 1933.

After her husband's death, Dorothea began a relationship with Ronald Joseph Sullivan. He had served in World War I and was awarded the Military Medal for bravery. Although they never married, they had two children together. While living with Sullivan, Dorothea started taking in elderly and sick patients. She turned her home at 32 Devon Drive in Nottingham into a nursing home.

Dorothea Waddingham ran a nursing home in Nottingham where two of her patients, Mrs. Louisa Baguley and her daughter Ada, became her focus. Ada Baguley had a history of health issues and had changed her will to leave her estate to Waddingham and her partner, Ronald Sullivan. Shortly after this new will was drawn up, Mrs. Baguley died in May 1935.

Ada continued to live until September, when she was reported to be in a coma. The next day, a doctor found her dead. The doctor did not suspect foul play based on Waddingham's details. Waddingham claimed that Ada's death was due to cardiovascular degeneration. However, Ada had instructed that she be cremated, which required two doctors to sign the death certificate. Waddingham misled the situation, saying there were no relatives to notify.

Cyril Banks, the Medical Officer for Health, became suspicious of Waddingham’s nursing home and ordered a post-mortem for Ada. The autopsy revealed high levels of morphine in Ada's body. The investigation then led to the exhumation of Mrs. Baguley's body, revealing that she also had died from morphine poisoning. This caused authorities to suspect Waddingham and Sullivan, eventually leading to their arrest.

Waddingham's trial began in early February 1936. During the trial, damaging evidence was presented, including details about Ada's last meal, which was inappropriate for her health condition. Waddingham was found guilty of the murders of both women on February 27, 1936. Sullivan was discharged due to insufficient evidence against him.

Despite pleas for mercy due to her being a mother of five, Waddingham was sentenced to death. She confessed to her crimes shortly before her execution. On April 16, 1936, she was hanged at Winson Green Prison. At the time, ten thousand people protested outside the prison against her execution, emphasizing public concern for her as a mother.