Reflecting again on the question David Runciman asked me on Friday ("How bad is this result, historically, for British liberals?"), I think the deep parallel is 1931. After thirty years of defending free trade against the populism of the Tory right, the dam finally burst.
As Labour turned to the left and the Liberals struggled to recover from previous setbacks, disaffected voters concluded that Protection was worth a shot. Most economists knew that it wouldn't revive the depressed areas, but the siren song of economic nationalism was irresistible
WWI hit Liberals hard at an emotional level (as Michael Bentley has shown in The Liberal Mind) but I think it was 1931-2 that sealed the collapse of 'Liberal England' and forced the party to accept a new political economy. Harking back to the glory days of 1906 was futile
In fact, I'm not sure the party ever really came to terms with it. Part of the appeal of Keynesianism (and, later, European integration) was that it allowed Liberals to avoid facing up to the way 1930s economic nationalism underpinned the post-war settlement.
I think this point just about comes through in my book on The Liberal Party and the Economy, but reading @DEHEdgerton on The Rise and Fall of the British Nation has helped me see it much more clearly
