This althistory covers a rarely explored aspect of WW2 counterfactuality - an UNsuccessful invasion of Britain in 1940, and the consequences it could have entailed.
24th May, 1940: The German 4th, 6th and 18th Armies, rather than halting as OTL, continues its pursuit of the retreating BEF. The ground around Dunkerque is unsuitable for tanks, and advance is slow.
26th May: Despite ferocious resistance, the Germans capture Lille.
27th May: Belgium surrenders. Lord Gort of the BEF requests an evacuation from Calais and Dunkerque. French counterattacks around Abbeville are halted.
28th May: Soldiers are sporadically lifted from the north coast of France. The Gremans take Ypres. Calais surrenders.
30th May: The remaining BEF in France are massacred to a man. Only 62,000 have escaped. The Germans have lost around 40,000 dead.