Rufus had fled, rendering any further defense of London City meaningless.
The only path left was to force a decisive battle with his father, Conqueror William, as soon as possible, and destroy his main army.
He had received word that his father was in Leicestershire.
To keep his father in the dark and ensure he still believed Robert's main army was in London City, he did not take the most direct route from London to Leicestershire, choosing instead to march through the Pennine Mountains.
However, he had vastly underestimated the difficulties of marching through such rugged, narrow mountain terrain.
To make matters worse, he encountered a flash flood during the march. He was forced to abandon all his wagons and march on with only the food their horses could carry.
Many warhorses and pack animals died during the march. By the time they were about to enter Leicester, their food had completely run out.
