Leaked U.K. diplomatic cables critical of President Trump have led Britain’s ambassador, Sir Kim Darroch, to announce his departure from Washington earlier than expected. But the story is not yet concluded.

According to one current and one former U.S. government official speaking on the condition of anonymity, Darroch repeatedly leaked classified U.S. intelligence information, including highly classified information, to a journalist for a U.S.-based media outlet. The sources are confirmed by the reaction my related inquiries have received from other government officials.

These leaks are unrelated to the diplomatic cables which sparked Trump's anger and Darroch's departure.

Still, one source says that the U.S. government was so alarmed by Darroch's leaks that it launched an official investigation to find the source of the information. That source described the leaked intelligence as “very sensitive,” and suggested that exigent U.S. security concerns motivated the investigation. That source says that non-U.S. government derived records showed the ambassador and journalist exchanging messages on a continuing basis. The source emphasized that these communications were not derived from U.S. government actions.

A second source, a career government official, described the leaks as "unprecedented."

The Washington Examiner has been unable to confirm how long any investigation continued or whether it has since been suspended. But concern inside the U.S. government over the leaks was significant.

One of the sources said that the ambassador repeatedly transmitted highly classified U.S. originator-control intelligence information to the journalist. ORCON intelligence, as it's called in the intelligence world, is closely held and carefully distributed. At least some of this information was classified at the "Five Eyes" alliance classification level, meaning it was distributed by the U.S. only to Australia, Britain, Canada, and New Zealand. Some intelligence may also have been classified at the U.S.-U.K. only level. Such intelligence is transmitted only on the condition of established protocols and the assumption it will be closely held.

The implications here are thus significant for two reasons.

While there is no indication that Ambassador Darroch was targeted as an investigative subject, even if incidental to Darroch, any investigative attention toward a British ambassador will raise eyebrows. Five Eyes protocols prohibit intelligence monitoring of allies. While this rule is occasionally bent, its malleability is tempered by the need to sustain shared trust.

Conversely, were the ambassador of America’s closest ally found to have leaked highly classified U.S. intelligence, it would undercut the trusting relationship of the two closest allies.

Yet it must be said that this risk is not new.

While U.S. and Britain retain the closest and most successful intelligence relationship of any two nations (near-symbiotic between the U.S. National Security Agency and its British counterpart, Government Communications Headquarters), sensitive leaks in media have occurred repeatedly on both sides of the Atlantic.

Following the May 2017 suicide bombing of a concert in Manchester, England, U.S. media leaks of British intelligence led Britain to temporarily suspend the sharing of certain intelligence material with the U.S. government. At the time, Trump described those leaks as "deeply troubling" and said that Prime Minister Theresa May was "very angry." In 2006, British intelligence officials were similarly enraged by U.S. action against al Qaeda operations officer Rashid Rauf at the culmination of an investigation into a plot against a transatlantic passenger aircraft departing Britain.

Still, for both nations, there is perhaps some solace here. Darroch has announced he will leave his post once a successor is appointed.

The White House and Justice Department declined to comment. As of publication the British Embassy did not respond to a request for comment.