Simon Case, the UK's highest-ranking civil servant from 2020 to 2024, has warned that leadership uncertainty is "enormously disruptive" and presents a "big challenge" for the government. Speaking to the BBC's Sunday with Laura Kuenssberg, Case highlighted that political upheaval "costs us money" by driving up borrowing costs, as markets respond to the possibility of a leadership challenge. His remarks come after Andy Burnham's victory in the Makerfield by-election, which has paved the way for a Labour leadership challenge against Sir Keir Starmer.