To me a BBC documentary "Necessary War" was in many ways revelation. This documentary explains why the British part in WW2 was tragically necessary. Without the British participation in both World Wars the present day Europe would have been a sad place. [media]https://www.youtube.com/watch?v=Pg5LWHQYIrY&index=3&list=WL[/media]
You mean in WW2 Churchill that gave the strength and will to fight to the nation? And there were also many other nations and men taking part, making the iron fist that lead to victory.
I agree British participation in WW II was vital to Europe as a whole, but not sure I agree about the Great War. Without Britain, Imperial Germany defeats France in 1915, possibly 1914. Germany gets a few overseas colonies (Africa/Indochina) and possibly a bit more of Poland. The US remains at peace as well as Italy possibly. There might not be a October revolution in Russia. The Hapsburgs and Ottomans might stagger on for a few more decades. No Mussolini, No Hitler. No Holocaust. No Atomic bomb.