In Order of the Phoenix, Harry saves Dudley's life by casting a patronus to drive back a dementor that was attacking him. Unfortunately, no good deed goes unpunished and he receives a letter that begins like this (emphasis mine):

Dear Mr Potter,
    We have received intelligence that you performed the Patronus Charm at twenty-three minutes past nine this evening in a Muggle inhabited area and in the presence of a Muggle.

It is my understanding that the Trace only lets the ministry know when magic is used in the vicinity of an underage wizard, and not specifically who did it or the circumstances surrounding it (that's why Harry got in trouble when Dobby cast a hovering spell in the Dursleys' house).

So how did the Ministry know that Harry cast a patronus in front of a muggle, and why didn't they also know that dementors were around?

  • 2
    Perhaps Umbridge sent in an "anonymous tip" Nov 17, 2016 at 20:12
  • 1
    I believe that by nature of trace it gets activates bunch of times. But given that dementors were send to attack him ministry was keeping close eye at Harry and thus tried to expel him from Hogwarts. The trace even within books doesn't always pick up magic but seams that he was close monitored. Nov 17, 2016 at 20:19
  • Corruption, plain and simple. Nov 17, 2016 at 22:32
  • 1
    Maybe they just assumed it was in front of the muggle, given that Harry is the only wizard in his place.
    – Lit
    Nov 17, 2016 at 22:55

1 Answer 1


I am going to speculate a bit here.

Remember that Dolores Umbridge, an employee of the ministry ordered the dementor attack. It may have simply been that she figured that kicking Harry out of school was an good backup plan since Harry wasn't destroyed.

Dolores did know there were dementors around, but it seems likely she was hoping Harry wouldn't have enough evidence to prove this. If Mrs. Figg hadn't been monitoring Harry, this might have been the case.

It also seems possible she might have been monitoring it more directly then what you get from a basic trace, and so knew what had happened pretty quickly.

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