History. 2 of 9. Stanley Baldwin called an election about six months in, in 1923, and Theresa May nine months in, in 2017. Both wanted support for a new policy. The other seven did not call one in their first year.
Hunch.
The June 2027 market resolves on the same GOV.UK page: YES if, between 25 September 2026 and 30 June 2027, the Prime Minister or Downing Street announces the date of a UK general election or says the King has been asked to dissolve Parliament, even if polling day is later. If GOV.UK is silent, BBC News and the Guardian reports of the announcement settle it.
We looked for cases where a UK prime minister took over between elections from a leader of the same party, with a working majority and at least two years before an election was due. We found nine since 1902. None of them called an election in the first five months. Two called one within a year, Stanley Baldwin in 1923 and Theresa May in 2017. Both said they needed support for a new policy, and both lost their majority.