During the Second World War, she worked for the Special Operations Executive, a British espionage and sabotage organisation.

[1] She studied at the French Lycée in London, and at age 17 she applied to join the Women's Royal Naval Service (Wrens).

[1][2] The F-section recruited and trained spies and agents to be dropped into France where they would sabotage Nazi operations and support the French Resistance.

[3][5][6] She wrote four novels (the Ardnakil Chronicles) based on her experiences in SOE: Katherine,[3] To live again, Before the dawn and Where love endures.

[6] Riols was appointed Member of the Order of the British Empire (MBE) in the 2023 New Year Honours for services to UK/France relations and World War II education.