As I said in an earlier thread, this harassment is going on in Feeders right now. As of yet, I haven't filed a Article 37 grievance, but I've documented every single instance of harassment. As someone above said, they will make your life miserable if you let them. I get called into the office about 3 or 4 times a week to discuss my "performance". I make it my mission in life to speak to them in a completely neutral tone of voice, and no get angry, because I know for a fact they are trying to get you mad/angry. Maybe you will blow your top, and curse them out, or maybe worse. Then they don't need to bug you about your times. Then they can fire you for alleged work place violence, whether that is verbal or physical.
I simply play as dumb as I possibly can, and tell them that I'm doing the best job that I can. But I'm not going any faster than I am now. It is a lesson that they are very slow to confront.
Whatever you do, don't lose your routine, resist the urge to cut corners, to speed up or lose your cool. If you show them that you follow their methods, work safe and stay consistent, they will eventually lose interest if you keep doing what you're doing. If you cut corners or speed up, they will see that their intimidation pays dividends. Don't give them the satisfaction.