Britain did not "separate" Israel and Palestine. Britain replaced Palestine with Israel. Please read the Balfour declaration. This did not start in 1948 but rather after World War 1 (1918)
Britain did this in attempt to expel its Jewish population. Britain was very anti-semitic at the time.
Rightfully Germany and Britain should give land to the Jewish population they force in Palestine.
But the opposite is happening.
I do understand that this has been a never ending debate and I appreciate your inputs on this. If you are keen on historical timeline, I have several notes that starts from 500BC, the Russian wars, WW1 and WW2 that links to the formation of Israel - Palestine today. For this note's purpose, we are only focusing post WW2