[5] During the 1930s, as part of the work they undertook to help Jews to escape from the Nazi regime, the sisters visited Germany on multiple occasions, using their enthusiasm for opera as a cover for their frequent travel, and smuggled Jewish people's jewellery and other valuables across the German border, thereby enabling Jews fleeing Germany to satisfy British financial security requirements for immigration.

[2] They worked with Austrian conductor Clemens Krauss and his wife, the Romanian soprano Viorica Ursuleac, who had initially told them of the persecution of the Jews.

During her career she wrote 112 romances for Mills & Boon, later re-edited by Harlequin Books, including the famous Warrender Saga, a series about the opera and concert-hall world.

But a good romantic novel is a heart-warming thing, which strikes a responsive chord in those who are happy and offers a certain lifting of the spirits to those who are not.In 1950 she published her autobiography, We Followed Our Stars.

[1][11] The same year, producer Donald Rosenfeld discussed plans to make a film of the sisters' humanitarian work and his efforts to unseal CIA files on their activities.

[citation needed] In 2024, the Cook sisters and their work rescuing German Jews were the focus of an episode of History's Secret Heroes on BBC Radio 4.