In 1320 Deken served as a schepen (an alderman) of Bruges and in that capacity became head of a delegation that went to negotiate with King Edward II of England on behalf of the Count of Flanders, Robert of Béthune.
In 1324, still a schepen, he again went on a diplomatic mission to England, this time by the order of Louis I, Count of Flanders.
In February 1328, Bruges rejected the re-appointment of the city magistrate proposed by the count's administration.
After the defeat Deken fled to Brabant, where he hoped to convince duke John III to rise against the newly crowned King of France Philip VI.
The Parlement of Paris convicted him of high treason, had his hands cut off, then had him dragged through the city streets and hanged.