In a damning exposé published Monday, The Intercept reporter Ryan Gallagher dives into the inner workings of National Security Agency's (NSA) largest overseas spying base, the U.K.'s Menwith Hill Station, and reveals concrete evidence that the British government is complicit in the United States' targeted killing program.

Citing top-secret documents obtained from NSA whistleblower Edward Snowden, Gallagher reports, "The files reveal for the first time how the NSA has used the British base to aid 'a significant number of capture-kill operations' across the Middle East and North Africa, fueled by powerful eavesdropping technology."

And given the British government's repeated assertion that activities at Menwith Hill "have always been, and continue to be" carried out with its "knowledge and consent," the findings are all the more damning.

"For years, Reprieve and others have sought clarification from the British government about the role of U.K. bases in the U.S. covert drone program, which has killed large numbers of civilians in countries where we are not at war," Kat Craig, legal director of London-based human rights group Reprieve, told The Intercept. "We were palmed off with platitudes and reassured that any U.S. activities on or involving British bases were fully compliant with domestic and international legal provisions. It now appears that this was far from the truth."

Built in North Yorkshire in the 1950s to spy on Soviet communications, the base experienced a rebirth after the 9/11 attacks and is now used "extensively to tap into communications in otherwise hard-to-reach areas," which includes countries outside of declared war zones, such as Yemen, Pakistan, and Somalia.

Menwith Hill is unique, as far as spy outposts go, because it pioneered programs specifically focused on "eavesdropping on communications as they are being transmitted through the air," which makes it a vital asset in targeting individuals in remote regions, such as northern Africa or the Middle East, who are more reliant on satellite communications.

The documents reveal two major surveillance capabilities at the site: one, called FORNSAT, "uses powerful antennae...to eavesdrop on communications as they are being beamed between foreign satellites"; the second, OVERHEAD, employs "U.S. government satellites orbiting above targeted countries to locate and monitor wireless communications on the ground below—such as cellphone calls and even WiFi traffic."

What's more, Menwith Hill "can harvest data from more than 300 million emails and phone calls a day," Gallagher reports, and—more worrisome—"pinpoint" the exact location of groups or individuals so that they can be captured or killed.

"The programs—with names such as GHOSTHUNTER and GHOSTWOLF—have provided support for conventional British and American military operations in Iraq and Afghanistan," Gallagher reports. "But they have also aided covert missions in countries where the U.S. has not declared war."

Gallagher continues:

The NSA’s documents describe GHOSTHUNTER as a means "to locate targets when they log onto the internet." It was first developed in 2006 as "the only capability of its kind" and it enabled "a significant number of capture-kill operations" against alleged terrorists. Only a few specific examples are given, but those cases give a remarkable insight into the extraordinary power of the technology.

Another document detailing the GHOSTWOLF project, according to Gallagher, provides the first concrete evidence directly implicating the U.K. in covert, lethal actions in Yemen.

British human rights lawyer Jemima Stratford QC told Gallagher that these documents show that the operations at Menwith Hill could have violated the European Convention on Human Rights, which specifically states that "no one shall be deprived of his life intentionally" except when found guilty in a court of law.

And Leeds-based Parliament member Fabian Hamilton said, "Any nation-state that uses military means to attack any target, whether it is a terrorist, whether it is legitimate or not, has to be accountable to its electorate for what it does."

"That's the basis of our Parliament, it's the basis of our whole democratic system," Hamilton continued. "How can we say that Menwith can carry out operations of which there is absolutely no accountability to the public? I don't buy this idea that you say the word 'security' and nobody can know anything. We need to know what is being done in our name."