Billy Prior is a fictional character in Pat Barker's Regeneration Trilogy of novels set during World War I.
Prior, often called by his second name, is an intelligent, deeply cynical soldier whom we first meet recovering from shell shock at Craiglockhart.
At the beginning of Regeneration he is temporarily mute, having found the detached eye of a dead comrade in the trenches, and mainly communicates through writing with pen and paper.
In the first novel of the series we learn that Prior was emotionally abused by his father, an abrasive wife-beater, an experience that also helped shape the man he would become.
Nahem Yousaf and Sharon Monteith called Prior "the mobilizing force in the trilogy; not only does he experience the war in phases, his chameleonlike character also facilitates shifts in perspective.