An all too frequent WWII alternate history cliché.
A particular favourite with pro-Nazi trolls. Supposedly, if Lord Halifax becomes PM then something approaching the abject surrender of Great Britain is presumed to follow. Realistically, while Halifax becoming PM raises the chances of a peace treaty the poms sure as hell were not going to sell themselves up the river.
This is neatly subverted in FletcherOfSaltoun's Halifax TL. While Britain and France are forced to make peace in 1940, both countries are soon back with a vengance and Germany gets squished…