Churchill was FURIOUS at what happened at Yalta ,yes.
And what happened at Yalta ( FDR selling out Eartern Europe),happened fore at least two reasons....FDR was dying and his "helper" a card carrying Commie,pushed him to give "Uncle Joe" anything he wanted.
Thank you for reconfirming what I thought I learned in my history class, oh a few moons ago. It looks like Chamberlain is not really a Churchillbuff.