Two UK teens were sentenced to a year in juvenile detention for plotting to blow up Buckingham Palace and the Houses of Parliament.

Authorities say that the two defendants had also discussed backup targets, which included a school and a shopping center.

Alleged ISIS Supporter Accused in Foiled Plot Was Turned in by Marine Dad

Last year, the teens bought chemicals like aluminum powder, sulfur and acetone, which were reportedly intended for making explosives. They also ordered fuses and pipes.

The mother of one of the teens called police after discovering the purchases. Police then began intercepting calls between the two boys, who were 15 at the time.

Sky News reported:

John Dilworth, Deputy Chief Crown Prosecutor for CPS North East, said afterwards: "It is alarming to note that, at the point when their scheme was discovered, these two young men had already secured all of the materials required to construct a viable explosive device.

"Thankfully, the potentially tragic consequences of their plans were never realized.

"We are grateful to the actions of the defendants' relatives, whose suspicions alerted police to the serious risk posed, not only to the public at large but also to the young defendants themselves."

Feds: NJ Man Planned to Join ISIS for $7K & Four Wives