From the Document: "On July 24, 2019, Boris Johnson became prime minister of the United Kingdom (UK) after winning the Conservative Party leadership contest that was triggered by the resignation of Theresa May as party leader on June 7. A colorful and polarizing figure who was one of the leading voices in the campaign for the UK to leave the European Union (EU), Johnson previously served as UK foreign secretary from 2016 to 2018 and mayor of London from 2008 to 2016. He inherits a government in which the Conservative Party controls a slim parliamentary majority by virtue of support from the Democratic Unionist Party (DUP), the largest unionist party in Northern Ireland."
CRS Insight, IN11150
Congressional Research Service: https://crsreports.congress.gov/