Certainty level: 100%
This relates to harassment at my workplace in Canada. Yes, "they" had their claws into my employers in North America, it doesn't just happen in England, it happens here as well.
During the second half of 1996, at work, I was sitting near a co-worker whom we shall call Mark Lee (we can, because that's his name). This guy occasionally came out with words and phrases that made me think that "they" had got to him and were supplying him with information about my home life (not social life please note, because of course I don't actually have a social life here).
During November 1996 I tried to catch him in the act of saying something "meaningful", a difficult exercise because as soon as he saw a tape recorder, he shut up completely, except for times when he knew he would be out of range of the walkman. (Note that the quality of this recording is not very good; I was just using a four-year-old tape walkman with a cheap microphone, quite low-tech).
During the evening of 12 November 1996, at home in my apartment (flat to you UK-ers), I said "life is so hard, and then you die". A nihilistic, negative thing to say, but quite distinctive. The following day, 13 November, Mark said loudly, "life is so hard eh, and then you die" followed by loud laughter.
In my book the precise repetition of the words makes this incident a 100% certainty. You, the reader, may differ, but then living in a free country allows each of us to have our own opinions, doesn't it?