Something curious happened in canon, where the Death Eaters knew enough about #12Grimwald Place to set up a vigil around it, but they couldn’t enter until one of the keepers actually showed them in, so Harry et al had to stand at the very edge of the wards and apparate everywhere. What’s curious about this is that it means Snape told them enough (or maybe it was Creacher? Hm.) to narrow down its location, but not enough to get in, and this never set off “Snape is hiding something” alarms among the Death Eaters. Which tells me that the naive interpretation where the secret dies with the original keeper was the common interpretation, but the Order of the Phoenix knew that it was much less secure than that and everyone who knew the secret became co-keepers on the original’s death. This also begs the question of what happens when all the keepers die (what happened with Godrick’s Hollow? The magical Graffiti implies that the Fidelius was broken altogether, not just by Voldemort).
So, according to canon, it’s still possible to lay siege to a place under the Fidelius, and the Death Eaters eventually broke in because Yacksly was grabbing Hermione when the trio made a return trip (How would that work with a small animagus, I wonder? Tracing wards probably wouldn’t work—the trace on underaged magic apparently wasn’t enough to get anyone in to any of the locations under Fidelius in Canon).
. What’s curious about this is that it means Snape told them enough (or maybe it was Creacher? Hm.) to narrow down its location, but not enough to get in
I think it was actually the constant use of the name Voldemort by Harry and Hermione, as they had not yet heard of the Taboo, that told the Death Eaters there was something worth investigating in the area.
Something curious happened in canon, where the Death Eaters knew enough about #12Grimwald Place to set up a vigil around it, but they couldn’t enter until one of the keepers actually showed them in, so Harry et al had to stand at the very edge of the wards and apparate everywhere. What’s curious about this is that it means Snape told them enough (or maybe it was Creacher? Hm.) to narrow down its location, but not enough to get in, and this never set off “Snape is hiding something” alarms among the Death Eaters. Which tells me that the naive interpretation where the secret dies with the original keeper was the common interpretation, but the Order of the Phoenix knew that it was much less secure than that and everyone who knew the secret became co-keepers on the original’s death. This also begs the question of what happens when all the keepers die (what happened with Godrick’s Hollow? The magical Graffiti implies that the Fidelius was broken altogether, not just by Voldemort).
So, according to canon, it’s still possible to lay siege to a place under the Fidelius, and the Death Eaters eventually broke in because Yacksly was grabbing Hermione when the trio made a return trip (How would that work with a small animagus, I wonder? Tracing wards probably wouldn’t work—the trace on underaged magic apparently wasn’t enough to get anyone in to any of the locations under Fidelius in Canon).
I think it was actually the constant use of the name Voldemort by Harry and Hermione, as they had not yet heard of the Taboo, that told the Death Eaters there was something worth investigating in the area.
Prediction: we shall see Fidelius Charm 2.0.