eight o'clock
While he was expressing his annoyance , General Foy , who had served against the duke in the Peninsula , rode up and said : `` Your majesty is distressing yourself without just reason , Wellington never shows his troops until they are needed . A patrol of horse will soon find out whether he is before us or not , and if he be I warn your majesty that the British infantry are the very devil to fight . '' The emperor soon discovered that the British were still in front of him ; for the English regiments were directed to clean their arms by firing them off , and the heavy fusillade reached Napoleon 's ears . At eight o'clock Wellington , who was anxiously looking over in the direction from which he expected the Prussians to appear , saw a body of mounted men in the distance , and soon afterward a Prussian orderly rode in and informed him that they were on the march to his assistance , and would soon be on the field . Grouchy had , in fact , altogether failed to intercept them . Napoleon had made up his mind that after Ligny the Prussians would retreat toward Namur , and sent Grouchy in pursuit of them along that road . That officer had gone many miles before he discovered the route they had really taken , and only came up with the rear of their column at Wavre on the morning of Waterloo .