She drew on experiences as a recent convert to Catholicism and having suffered hallucinations due to using Dexedrine, an amphetamine then available over the counter for dieting.

The novel's quick success enabled Spark to give up editorial work and devote herself to full-time creative writing.

Meanwhile her boyfriend Laurence, who has been staying with his grandmother in Sussex, discovers that the older woman is involved in smuggling, baking diamonds into loaves of bread.

Spark, a Catholic convert, had recently taken instruction and believed that the Comforters were really demons whose intention was to pour salt into Job's wounds.

The idea for the plot came to Spark after a serious mental breakdown, during which she believed that there were secret word game style codes in the poems of TS Eliot.

She finally became better as a result of improved nutrition (she had been chronically malnourished) and a rest cure funded by a number of writers, including Graham Greene.