The empire was an idea who's time had past, Britains
didnt want to be the slavemasters of the world.

Really?,I think the British empire officially ended during Suez crisis when US
told British rather unexpectedly (at least for the Brits) "stay at home or
else".
US engagement in WWII had two goals:
1)Defeating Nazi Germany
2)Destroying British Empire

Till Suez crisis Brits hoped that US might want to forget second goal,but US
had other plans.