Quotes from Franz Halder

The finishing off of the encircled enemy army is to be left to the Luftwaffe.

The left-wing, which consists of armoured and motorized forces and has no enemy in front of it, will be stopped dead in its tracks upon direct order from the Fuhrer.

The reason is that a military defeat of Britain will bring about the disintegration of the British Empire. This would not be of any benefit to Germany.