Experts say why they think it appears increasingly difficult for prime ministers to remain in power.
Rishi Sunak is the UK's third prime minister in less than two months - the fifth in six years. It is the fastest turnover of leaders in No 10 for nearly a century.
Jill Rutter, from the think tank the Institute for Government, believes the Brexit vote in 2016 has been the number one destabilising factor in British politics over the last six years. Mr Cameron's resignation after six years in office paved the way for Theresa May. She spent three years and 11 days in office, while her successor, Boris Johnson, spent three years and 44 days at the helm.and the fact that she and the party could not agree what Brexit meant," Ms Rutter adds.
"The membership had changed quite a bit," she explains. "They were ready for the message about ignoring orthodoxy. But they discovered when they went hell for leather against conventional wisdom, they fell over in a heap.""The referendum has destabilised British politics," he says. "The difficulty has been to find the right relationship with Europe.
Aged 42, Rishi Sunak is the youngest prime minister in more than 200 years. He has risen through the ranks of the Conservative Party in the space of just seven years since he was first elected as an MP in 2015."That has destabilised parliamentary politics.