He had to resume hostilities to maintain the balance of power

William Pitt was an extremely reserved, almost haughty person in public, but, in private was extraordinarily affectionate. He did not make friends easily, but Pitt held on tenaciously to those who managed to break past his reserve, and to a point where his Romantic friendships still puzzle scholars (ex. William Wilberforce, who became an outspoken opponent of Pitt's draconian policies during the Wars of the French Revolution but whom Pitt still considered one of his closest friends, and with whom Pitt had an odd but extremely enjoyable amount of slashy subtext in the 2006 film Amazing Grace).

Pitt was willing to bend over backwards for his family, as well, and adored his nieces and nephews. At one point, his niece, Lady Hester Stanhope blacked Pitt's face, while some other family members pinned him down, to amuse the youngest members of the family. This struggle, which evolved into a pillow fight, was interrupted by several members of Pitt's cabinet, including Lord Castlereagh. Pitt's transformation of demeanor was remarkable; he wiped off his face, and straightened up to the point where Lord Roseberry said that, after Pitt had assumed his working personna, "his tall figure seemed to stretch to the ceiling and all these powerful men who came calling bent like willows before him".

Immediately afterwards, Pitt resumed the pillowfight. One wonders if the Cabinet Ministers were asked to join in.