Halifax came within a whisker of becoming Prime Minister in May 1940; the job was his to refuse. The Tory Party, and the King both wanted him his place in House Lords was a barrier that could be removed.

This scenario describes in my opinion what would have happened if Lord Halifax had accepted the post.

May 1940 -

Lord Halifax becomes Prime Minister.
Germany invades France.

June 1940 -

France and Britain declare an armistice with Germany.
Italy who is eyeing Britain’s colonies all so reluctantly agrees.

July 1940 -

Soviets take Lithuania, Latvia and Estonia.

Oct 1940 -

Italy invades Greece and Yugoslavia.

April 1941 -

Germans invade Greece and Yugoslavia to aid their Italian allies.

June 1941 -

The Axis powers attack the USSR.

Oct 1941 -

Axis push towards Moscow begins.

Nov 1941 -

Axis forces surround Moscow.
Battle of Moscow begins.

Dec 1941 -

Soviet counter offensive begins pushing the Axis back to the North and South of Moscow and breaking the Axis ring of steel.
The Axis forces however manage to keep the path to Moscow open.

To be continued -