London, which has been the centre of political power in the UK for centuries, is by far the leading region of birth of UK Prime Ministers with 31% of all Prime Ministers born in London. This is well ahead of it's share of the UK population over the period. This was particularly true before the 20th century when it was the region of birth of 41% of Prime Ministers. Pre-20th century Britain was even more centred around London than today. As ease of travel has increased in the 20th century, more Prime Ministers have been born outside of London. Only 1 of the last 9 Prime Ministers, David cameron, was born in London.

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There were 20 British Prime Ministers in the 19th century. 10 were born in London. In the first half of the 19th century, the Tory and Whig party were dominant. In the 2nd half, the Conservative (now often called Tories) and Liberal Party became dominant. 

In the 20th century, Scotland and the Southeast have overtaken London as the region of birth of most Prime Ministers. Both of the last 2 Labour Prime Ministers, Gordon Brown and Tony Blair, were born in Scotland although Tony Blair was primarily raised in England. The majority of 20th/21st century Scottish born Prime Ministers are from the Labour Party. Quite remarkably, there has yet to be a British Prime Minister born in Wales. David Lloyd George is generally regarded as a Welshman though. Although he was born in Manchester, his parents were Welsh and spoke Welsh as a first language. There has also yet to be a Prime Minister born in Northern Ireland. However, 2 Prime Ministers were born in Ireland during the 19th century when the whole of Ireland was part of the UK. They were William Petty and Arthur Wellesley, 1st Duke of Wellington. 

The wealthy Southeast region has been by far the most common region of birth of Prime Ministers after the second world war. 5 out of 13 postwar Prime Ministers were born in the Southeast. This reflects the often mentioned complaint that there is too much power in the Southeast of England. 4 of the Prime Ministers born in the Southeast were from the Conservative party which reflects their strength in the region. Britain's most famous Prime Minister, Winston Churchill, was born in the Southeast at Blenheim Palace in Oxfordshire.

Notable is the lack of Prime Ministers born in the north of England. A significantly larger percentage of Prime Ministers were born in the Northwest before the turn of the 20th century compared to after, including William Gladstone. 2 Prime Ministers have been born outside the UK, both in North America. The current Prime Minister, Boris Johnson, was born in New York City, USA. The other was Bonar Law, a Tory Prime Minister between 1922 and 1923, who was born in Canada. Both moved to the UK as children. 

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Note: Although Robert Gascoyne-Cecil completed the last of his 3 terms in 1902, he is counted as a pre-20th century Prime Minister since he served the vast majority of his nearly 14 years as PM in the 19th century.