Under normal circumstances, the ruling party always chooses the Prime Minister under a parliamentary government. Thanks for reminding me of this point.
Since this is a what if thread, I thought of considering Atlee since the politics at that time was in flux. If we consider all possibilities, I think the King could've ordered the Parliament dissolved and called for new elections to settle things. Correct me if I am wrong but that's how I understand how a parliamentary government operates. I understand that England operates under a constitutional monarchy. In this context, is my opinion plausible? Your reply would further my understanding of the UK.

I guess since there's been no reply to my question, it's time for me to check out the British Council here to get some more background about this. This query of mine really intrigues me. I'll post what I learn from the guys and gals there.

So, for anyone else to emerge Halifax has to be unavailable. Halifaxes position in the House of Lords is susposed to have made him a poor candidate. Assuming he rejects the opportunity, or is rejected, then it is still not clear who would be the next choice.

I've pursued this question off and on for several decades and the two names that always come up are Halifax & Atlee. But, Atlee as a minority member has a weak chance at it & Halifax is also in weak position and reluctant. There must have been other powerful indivduals in the Conservative party who would have been available.

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That's how I read it too even with the limited knowledge I have of WWII British politics. I hope I can dig up something at the British Council.

Nothing, would have been the same.

Pilots & the Planes they fought not him. Nor did he had anything to do with the outcome.

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Sorry about the delay.
The King could dissolve parliament, and call new elections but this would be highly risky in wartime, and even if he did he would still have to ask the party with the largest number of MP's to form a government, and this would almost certainly have been the Conservative Party again.
Therefore the Prime Minister would still have to come from the ranks of the Conservative party.. Atlee is not an option.

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if in doubt....Panic!!!!

Rab Butler and Antony Eden are two that could have been considered.
Rab Butler would have sought peace, while Eden would have wished to continue with the war.. but without a leader with the personality of Churchill and his ability to inspire both parliament and the general population, I don't see anyone with the ability to raise the support needed to continue the war.

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if in doubt....Panic!!!!

Thanks for the additional names. I'll include them in my research, Redcoat.

Now we are getting somewhere. So it is not impossible a British leader would at least hold some preliminary talks (probablly secret) with Germany, and that might lead to real negotiations. The alternate would be rejection of imeadiate peace talks, but a less focused or cohesive government continuing the war.

In either case what changes when Germany attacks the USSR in 1941?

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After looking into this more closely, it would seem that the next best choice would be Anthony Eden. Eden and Churchill both led factions within Chamberlain's party. Eden also gained stature after he resigned when Chamberlain followed through with his appeasement policy with Italy. Unfortunately for Eden, after he resigned, he was not as publicly vocal as Churchill. Eden acted more like a refined aristocrat who was watchful of what he would say while Churchill had the gift for gab. The two were rivals and hardly got along while Chamberlain was in power but they shared the same views and principles.
So, from what I was told by the helpful folks during my visit to the British Council at Ortigas Center, it would seem that it is possible that Eden could have been PM if for some reason or another, Churchill suddenly was not available to take over from Chamberlain. To be fair to Churchill, once Churchill took over, he took in Eden and the two became confidants.

To be frank, the guys at the British Council did laugh when I asked about this because they never considered such a possibility. Fortunately, they were intrigued by the idea that they went into a discussion of British WWII politics, to which I was a rapt listener.

As to Rab Butler, I was told that he was too identified with Neville Chamberlain. Most of the government executives or politicians that supported Chamberlain's appeasement policy had to lay low or were shunted to less important responsibilities after Chamberlain fell.

This is excellent. I was unaware Eden had any role of importance in those days. Thought he came to prominence later, which shows how ignorant I am.

That the group you spoke with ahd never considered this question suprises me. Evidently they are not alternative history fans.

Anyway it looks like the leaders favoring peace all had fairly weak positions, and there was at least one prowar alternative to Churchill. Leaving aside dark horses abruptly rushing to the lead, it appears the prowar faction is the favorite for suplanting Chamberlains government. Further, if the peace factions attain power they are likely to depend on some fairly weak leaders in front, so that post Barbarosa Britian may still reenter the war against Germany.

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Didn't Churchill give Chamberlain a government post later on?

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According to the Conservative party rules in this period the successor was chosen by the outgoing leader( it would then be up to the senior members of the party to agree with it, normally this was a given)
It was Churchill who later moved those who supported the appeasement policy too readily, if Rab Butler had been appointed this wouldn't apply.

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if in doubt....Panic!!!!

If Halifax hadn't refused the appointment of PM when it was offered to him. he would have been Prime Minister.

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if in doubt....Panic!!!!