"The evening is the great time, isn't it, Alex boy?"
P. R. Deltoid, is Alex's Post-Corrective Advisor who is assigned to him after his time at a corrective school. He is seen checking up on Alex at his house without forewarning him. It is implied Deltoid may have a predatory nature as he smugly urges Alex to sit with him and proceeds to touch him inappropriately.
His main motivation for looking after Alex is the effect that his arrest and prison sentencing would have on Deltoid's reputation. During Alex's interrogation following his arrest, Deltoid comes to see Alex spitting on his face before leaving. The last Alex sees of him is during his trail when he gives evidence against him.