But does the First Past the Post system usually deliver the leader of the party with the most votes and the most seats into Number 10?
If we look back over the years since 1900, we can clearly see that this has not always been the case.
In the 1900 election the Conservatives won over 400 seats, but in 1905 they left office before the next general election. The Liberal leader Campbell-Bannerman became prime minister, although his party had fewer seats. In the 1906 election the Liberals won a landslide victory and normal First Past the Post service resumed with the Liberals having won the most votes and the most seats and Campbell-Bannerman remaining as prime minister.
However, it was not long before ‘abnormal’ conditions prevailed again. In the January 1910 election the Conservatives won the most votes, but the Liberals won the most seats and remained in office with the support of Labour and the Irish Nationalists. The next election in December 1910 left the abnormal situation in place and so it continued into the First World War.
In 1916 Lloyd George became prime minister of a coalition government. He was a Liberal, but not the Liberal Party leader. At the end of the war, the 1918 election delivered the premiership back to Lloyd George, who was still not the leader of the party with the most votes or seats.
Briefly from 1922 to 1924 the government was formed by the Conservatives, as the party with the most votes and the most seats and their leader served as prime minister.
But in 1924 the Labour Party formed their first government, without a majority of seats or votes. It lasted for ten months.
Between the end of 1924 and 1929 the Conservatives formed the government as the party which had won the most votes and the most seats, but the 1929 election heralded another ‘anomaly’. The Labour Party under Ramsay MacDonald returned to power, but still with fewer votes than the Conservatives. In 1931 the second Labour government collapsed, but Ramsay MacDonald remained as prime minister of a National Government until 1935. In May 1940 Churchill, not the Conservative Party leader at the time, became prime minister, although he did assume the party leadership five months later.
From 1945 to 1951 Labour leader, Attlee served as prime minister as head of the party with the most votes and the most seats. But the 1951 election delivered the premiership back to Churchill even though the Conservatives had won fewer votes than Labour.
‘Normal’ service was then resumed from 1955 to 1974 with the leader of the party with the most votes and seats serving as prime minister. But after the February 1974 election Harold Wilson became prime minister, although Labour had won fewer votes in the election.
During the ABBA era and beyond the leader of the party with the most votes and the most seats has served as prime minister.
In total since 1900 we have had 25 years when the prime minister was not the leader of the party with the most votes and the most seats, so we should not be too surprised if this happens again next month.