[3] For his fifth book, Dr. Cronin drew on his experiences practising medicine in the coal-mining communities of the South Wales Valleys, as he had for The Stars Look Down two years earlier.

He had also worked as a doctor for the Tredegar Medical Aid Society at the Cottage Hospital, which served as the model for the National Health Service.

Cronin once stated in an interview, "I have written in The Citadel all I feel about the medical profession, its injustices, its hide-bound unscientific stubbornness, its humbug ...

Resigning, he obtains a post as assistant in a miners' medical aid scheme in "Aberalaw", a neighbouring coal mining town in the South Wales coalfield.

Eager to improve the lives of his patients, mainly coal miners, Manson dedicates many hours to research in his chosen field of lung disease.

Seduced by the thought of easy money from wealthy clients rather than the principles he started with, Manson becomes involved with pampered private patients and fashionable surgeons and drifts away from his wife.

There are also three film adaptations of the novel in Indian languages: Tere Mere Sapne (1971) in Hindi, Jiban Saikate (1972) in Bengali and Madhura Swapnam (1982) in Telugu.