A large part of police undercover surveillance is utterly ludicrous.
I remember in the 1980s running an open seminar on the theme capitalism and crisis. A well dressed young man turned up, a complete blockhead, who showed an interest in obtaining copies of every handout I had. He seemed most keen to know when we were moving on from talk to action.
A few days later I received a fat envelope containing all my handouts neatly stapled together, with a note from the fellow saying he was no longer interested.