How is anachrony used in The Girls of Slender Means by Muriel Spark?

The Girls of Slender Means by Muriel Spark uses anachrony in the form of flashbacks to the climactic event, which greatly affects the lives of the characters. This event is a fire in a dormitory building caused by a detonated bomb combined with the rupture of a gas line.
The flashbacks and vignettes that show how the events unfolded is a device used by Spark to explore each character in depth. Each of the characters respond in different ways to the chaos and tragedy. Some are selfish, like Selina Redwood, whilst others die due to poor decision-making.
The device of anachronism is also used to show how some of the characters—such as Nicholas and Joanna—change after the traumatic event. Additionally, the time period in which the story is set gives the novel a historical feel, which is complimentary to the anachrony used to portray the events and the people involved.