Interesting historical analysis here hinting that the idea that a Left-leaning Labour Party can’t win over the country in an election may well not in fact be true.
Perhaps winning a war improved Thatcher’s standing, and Foot suffered because of that rather than because of his policy? Perhaps it was the more right-wing splitters the SDP that pulled away Labour’s vote-base?
I’m pretty sure anyone thinking a Leftist Labour Party can’t ever win at all is simply wrong. Circumstance and luck play as big a role as policy ever did. Whether they have the solidarity and enthusiam to do it over the next five years, we shall see.