He fell under the influence of an inferior servant of his house, Peter de la Brosse, who had been surgeon and barber first of all to St.Louis and then to Philip III., who made him, before long, his chancellor and familiar counsellor.

Being, though a skilful and active intriguer, entirely concerned with his own personal fortunes and those of his family, this barber-mushroom was soon a mark for the jealousy and the attacks of the great lords of the court.

And he joined issue with them, and even with the young queen, Maria of Brabant, the second wife of Philip III.

Accusations of treason, of poisoning and peculation, were raised against him, and, in 1276, he was hanged at Paris, on the thieves' gibbet, in presence of the Dukes of Burgundy and Brabant, the Count of Artois, and many other personages of note, who took pleasure in witnessing his execution.

His condemnation, "the cause of which remained unknown to the people," says the chronicler William of Nangis, "was a great source of astonishment and grumbling." Peter de la Brosse was one of the first examples, in French history, of those favorites who did not understand that, if the scandal caused by their elevation were not to entail their ruin, it was incumbent upon them to be great men.
In spite of the want of ability and the weakness conspicuous in the government of Philip the Bold, the kingship in France had, in his reign, better fortunes than could have been expected.
The death, without children, of his uncle Alphonso, St.Louis's brother, Count of Poitiers and also Count of Toulouse, through his wife, Joan, daughter of Raymond VII., put Philip in possession of those fair provinces.