The Battle of Britain Five Months That Changed History, May—October 1940 by James Holland (z-lib.org).epub

Daladier and Gamelin, Churchill, for one, could not accept that France had
passed the point of no return. After all, they still had vast numbers of
troops, thousands of artillery pieces, and many, many tanks. If only a
counter-attack could be quickly planned and executed, then surely the
lightning German advance could be stalled. And while there was a chance,
he believed Britain had a moral obligation to stand by her ally. On the other
hand, if he was wrong, and it was too late for France, with every British
fighter plane that was shot down across the Channel, Britain’s own chances
of survival were diminishing.
Such were the terrible, impossible conundrums facing the British in
May 1940.