Shirk said that for almost two decades China’s rulers had abided by an unofficial succession system designed to prevent both cut-throat and destabilising internecine power struggles and the rise of strongman dictators who could cling to power until they died or were violently overthrown.

According to those unwritten rules, presumptive heirs to the Communist party’s top two jobs, general secretary and premier, should be informally anointed five years ahead of a full leadership transition, as had happened with Xi and Li in 2007.

Some had seen Sun as one of those two likely heirs – the other was Guangdong party chief Hu Chunhua, who remains in power – and the decision to bring him down now brought “intense uncertainty about how the game will be played in the future”, Shirk said. “I think that has got to make the people at the top ranks of the Chinese communist party very uneasy about the risks that presents.”