The million-dollar question:This entire post is interesting to me, because it shows a possible response to an unresolved historical dispute. When historians cannot achieve a general consensus, an ordinary person turns to the Internet for an answer.
With General Gerd von Rundstedt's panzers less than 20 miles from the British Expeditionary Force (BEF), why did Hitler agree to (sanction) a stop order that originated from von Rundstedt? I have no clear answer despite reading more than 5 articles on the Net. This article - The miracle of Dunkirk
http://www.telegraph.co.uk/culture/tvandradio/7724309/The-miracle-of-Dunkirk.html - suggests three theories. It boggles my mind that theories, instead of clear-cut answers, abound and that historians differ in their analysis and opinion.
Maybe the answer lies here: https://www.quora.com/Why-did-Hitler-halt-the-advance-on-Dunkirk-for-48-hours
Ah now I am getting warmer. A German historian reached the conclusion that the reason why Hitler remained unmoved on the hotly contested halt order, was because he wanted to show his German High Commanders who was boss. Megalomania. Sounds highly plausible. What say you Agent Scully and Moulder?
http://www.ibtimes.co.uk/dunkirk-75th-anniversary-real-reason-hitler-let-british-troops-go-1503201