I just want to make a point that I think is important. On the 22nd of July the warsaw uprising hadn't happened yet, and that was an event that brought home to the west just how cynical Stalin could be. Admittedly they decided to let Stalin have his way, but one poster said that the british "Were happy to abandon Poland". This was simply not true - the situation was that certain elements of british government were rabid stalinists, but the warsaw uprising brought home to churchill (and perhaps alanbrooke) how ruthless Stalin was, and how he would ignore protesters who could not affect him (summed up by his quote "How many divisions does the pope have?").

But the point I'm trying to say is that by 22nd July the Red army was not deep into eastern europe, and the split that caused the Iron curtain speech had not happened yet. An assaination of Hitler on that date might have ended the war sooner, but the brits wouldn't have teamed up with the Germans against the Russians (And neither would the americans).