I remember in senior school one of my friends who was a prefect used to date one of Ronnie Kray’s bodyguards who owned a variety of bullet-proof vests.
It seems that at the time these vests contained ceramic plates which were able to absorb most of the bullet’s energy on impact.
Well as it happened this prefect had a bit of a run in with the senior mistress for reasons which are still sketchy, and an appointment was arranged for a meeting in her study. Since it was London to a brick on that a meeting in the office of the senior mistress would involve a very good session with the Lochgelly our young friend decided to take suitable preemptive measures.