Lucia in Wartime (1985)

Lucia in Wartime is the seventh book in Mapp and Lucia series and the first novel to be written by another author.

Synopsys
Across the Channel, the battle rages ... On the Tilling front, another battle is being fought-the constant war of wits and social ascendancy between Lucia Pillson and Elizabeth Mapp-Flint. Lucia, with her superior style, timeless elegance, occasional low cunning and husband Georgie-whose talent for transforming powdered eggs and canned meat into gourmet fare has turned him into a minor celebrity-invariably wins the day. Although Elizabeth may have lost a battle or two, she definitely hasn't lost the war-until she carelessly gives Lucia the ultimate weapon against her, upsetting the balance of power in Lucia's favor. But how long will Lucia be able to retain the admiration of all Tilling if her power remains unchecked? After all, absolute power corrupts absolutely.