2 cleanup, correct attributed quote
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When asked, JK Rowling responded saying: It's been there as long as the Ministry itself

The Veil is the barrier between the land of the living and the land of the dead. One cannot travel freely between the two worlds, as it is a one-way trip. Inexperienced wizards know nothing about it, but the much more experienced wizards may have heard about it, and the Unspeakables who work in the Department of Mysteries have likely studied it closely.Siruius Black falling through the veil

Source:As stated on the WikiaVeil page on the Harry Potter Wikia:

The Veil is the barrier between the land of the living and the land of the dead. One cannot travel freely between the two worlds, as it is a one-way trip. Inexperienced wizards know nothing about it, but the much more experienced wizards may have heard about it, and the Unspeakables who work in the Department of Mysteries have likely studied it closely.

Siruius Black falling through the veil

When asked, JK Rowling responded saying: It's been there as long as the Ministry itself

The Veil is the barrier between the land of the living and the land of the dead. One cannot travel freely between the two worlds, as it is a one-way trip. Inexperienced wizards know nothing about it, but the much more experienced wizards may have heard about it, and the Unspeakables who work in the Department of Mysteries have likely studied it closely.Siruius Black falling through the veil

Source: Wikia

When asked, JK Rowling responded saying: It's been there as long as the Ministry itself.

As stated on the Veil page on the Harry Potter Wikia:

The Veil is the barrier between the land of the living and the land of the dead. One cannot travel freely between the two worlds, as it is a one-way trip. Inexperienced wizards know nothing about it, but the much more experienced wizards may have heard about it, and the Unspeakables who work in the Department of Mysteries have likely studied it closely.

Siruius Black falling through the veil

1
source | link

When asked, JK Rowling responded saying: It's been there as long as the Ministry itself

The Veil is the barrier between the land of the living and the land of the dead. One cannot travel freely between the two worlds, as it is a one-way trip. Inexperienced wizards know nothing about it, but the much more experienced wizards may have heard about it, and the Unspeakables who work in the Department of Mysteries have likely studied it closely.Siruius Black falling through the veil

Source: Wikia