Lincoln:
I must hold my hand out for this one! I assumed the "Dunkirk Victory" was meant as a joke, but had no idea the phrase had such a distinguished pedigree! Having said that, Field Marshall Gort (the BEF c-in-c) deserves a lot of credit for realising the French were on the point of collapse and being determined to rescue the British Army. I think it was Montgomery who said that the real victory was that the troops lived to fight another day, which they did to no mean purpose. Something to think about yesterday and tomorrow at 11.00 am.
Living here 'across the Pond,' I've only seen a few British television comedies on occasion, "Dad's Army" not being one of them; however, I did suspect that the remark about Dunkirk might have been meant sardonically (as a commentary on wartime propaganda)--but in that it case I figured that it was 'pushing it' to have one of the story's characters predict a probable British triumph by Christmas after the British Expeditionary Force had been driven from continental Europe.
Undoubted Adolf Hitler would've at least have approved of the German halt order at Dunkirk, even if he hadn't originally given it, but IMHO it was more of a political decision than a military one. Hitler underestimated the British will to continue fighting, he expected (or at least strongly hoped) to co-opt the British Empire in a 'crusade against Bolshevism'--something he undoubtedly felt would be more likely to occur if the Germans didn't slaughter many thousands of British troops on the beach at Dunkirk.
Even after Dunkirk, it's quite possible that the Germans could've won the war if they'd dropped all the paratroopers they had into southern England and captured a couple major airfields, so that the Luftwaffe could fly in reinforcements and equpment before the B.E.F. could be resupplied. However, for all of his blustering, AFAIK Hitler never seriously planned on invading Great Britain--nor was he ever convinced to commit sufficient German resources to north Africa to capture the Suez Canal, which would've seriously undercut the British ability to fight effectively in the Mediterranean area.
BTW, General (later Field Marshal) Bernard Montgomery was prone to exaggeration (IMHO), I recall that he referred to 'Operation Market Garden,' the last major Allied defeat on the western front in Europe, as "ninety percent successful."
Your forces didn't cross the Rhine, Monty, so it wasn't successful at all... --C.K.