To prevent Her Maj from taking over, I expect :) And I'm only half-joking - when they set the rules up, they were desperately trying to avoid being re-annexed by the Brits.
It's supposed to prevent the president from straying in allegiance to the US and it is designed to protect our sovereignty...which is really quite hilarious given the level of institutionalized campaign finance corruption we tolerate.
When was your last non-UK born Prime Minister?
Thought this was addressed to a Brit but maybe to me?
Last non-Canadian born PM was John Turner who ended his term in 1984. Born in England which is not part of our country and there is no requirement for Canadian or UK birth. Interesting coincidence that we have not had a non-Brit Empire born PM, but since only 4 PM have not been Canada born, not too surprising? The other three were long ago.
I wasn't contrasting US with Canada but simply interested in the utility of the requirement for US born.
That's what illustrates the point of the OP, Unseen. I don't know which PM's of the UK were born where, because it's not a prerequisite for candidacy. Nobody actually cares. There could never be a situation like the one here in the US where after the President took office, there were demands for sight of his birth certificate.
It may well stem from the fact that you have a fixed written constitution, whereas the nearest we have to one in the UK is the Magna Carta signed in 1215, and the law is updated continuously with judicial precedent. Perhaps at the time the US had declared its independency, there was a need to stipulate rules to underscore that, such as the birthplace of the President, etc..
To add to that, the people in the UK do not vote to elect the Prime Minister. They simply vote for the party of choice. It is the party itself that has nominated its own leader. The party can change its leader mid term, without reference to the electorate. This happened in recent memory when Margaret Thatcher was replaced by John Major, and again when Tony Blair was replaced by Gordon Brown.
When that law was written, it was because we had just gotten out of a war with England, and Many of the citizens were still loyal British citizens as well. They wanted to make sure that the country couldn't be hijacked by planted candidates from other countries. Nowadays, it seems that rule just fuels racist birther idiots.
That law seems a little dated since we are a country of immigrants. I do think, however, that some sort of stipulation, like having lived here for 20 or 30 years isn't unreasonable.
Not disputing your assertion of reasonableness, but wonder if you might expand on that?
We also have that in my country. We do this in order to guarantee that the candidate is aware of the problems the city is facing and (more likely speculation) to preserve political power among same and opposing party members.
President must currently be at least 30 years old, and must have spent 14 of those years in the states, as well as must be a naturally born citizen.