Magic on Privet Drive

[Tandra]

No: HPFGUIDX 168298

Ok so I've just stared reading OoTP again. (for the second time in a
month and a 1/2 lol) And IDK why I didn't see it before, but if
Harry's house is under such surveillance, then how did his Guard get
away with all the magic that was being done in the house?

Yes I know they were all of legal age, but shouldn't the ministry have
detected the use of magic in the house at that point? Especially after
Harry had just done magic not too long before. Wouldn't it be under
closer scrutiny? 

If anyone has an answer to this please let me know.

Tandra