The delay was fatal to Napoleon's plans.
Had the battles commenced at daybreak, Ney could have brushed aside the defenders of Quatre Bras, and would have been at Mount St.Jean by the time the English came up.

The Prussians would have been beaten by noon instead of at dusk, and before nightfall their retreat would have been converted into a rout, and on the following day Napoleon's whole army would have been in a position to have fallen upon the only British divisions that Wellington could by that time have collected to oppose him, and would probably have been in possession of Brussels before night.
Thus, while the delay in sending news to Wellington prevented the allies combining against the French on the 16th of June, the delay of Napoleon in attacking that morning more than counterbalanced the error.

There was the less excuse for that delay, inasmuch as he had himself chosen his time for fighting, and should not have advanced until he had his whole force well up and ready for action; and as the advance during the first day's fighting had been so slow, the whole army might well have been gathered at nightfall round Fleurus ready to give battle at the first dawn of day.
Fighting as he did against vastly superior forces, Napoleon's one hope of success lay in crushing the Prussians before the English--who, as he well knew, were scattered over a large extent of country--could come up, and his failure to do this cost him his empire.
The artillery fire ceased in front before the column continued its march for Mount St.Jean.The Prince of Orange had paused in his advance when he saw how strong was the French force round Frasnes, and Ney was not yet ready to attack.

Therefore from eleven until two there was a cessation of operations, and the ardor of the troops flagged somewhat as they tramped along the dusty road between Mount St.Jean and Genappe.
The Prince of Orange was having an anxious time while the British column was pressing forward to his assistance.

As the hours went by he saw the enemy's forces in front of him accumulating, while he knew that his own supports must be still some distance away Nevertheless, he prepared to defend Quatre Bras to the last.