Peter Strzok, the FBI counterintelligence agent pulled off Special Counsel Robert Mueller's probe last year for sending anti-Trump / pro-Clinton text messages to his "lovebird" FBI mistress, played a more central role than previously known in both the Russia and Hillary Clinton investigations, a lawmaker told Fox News on Tuesday.

The assessment of Strzok's involvement comes after six hours of closed-door interviews with FBI espionage chief Bill Priestap, along with an analysis of "recent records."

Colleague Catherine Herridge rpts a mbrs familiar w/Hse closed-door i-view w/FBI espionage chief Bill Priestap has been cooperative. But says FBI Agent Strzok played an more central role than previously known in Clinton email/Russia investigations beyond Strzok/Page text messages — Chad Pergram (@ChadPergram) June 5, 2018

Priestap was interviewed Tuesday as part of an ongoing joint investigation by the House Judiciary and Oversight committees. Priestap was Strzok's supervisor and oversaw both the Russia and Clinton investigations. The lawmaker described Strzok as a very cooperative witness, but added that unanswered questions remained about Priestap's overseas travel. One line of questioning Tuesday concerned a trip to London by Priestap in May 2016 and whether it was connected to the Russia case. The trip was referenced by Strzok in a May 4, 2016 text message to FBI lawyer Lisa Page that said "Bill" would be "back from London next week." -Fox News

Strzok emailed Priestap on January 30, 2016 along with another colleague to express dismay about statements made by former White House Press Secretary Josh Earnest claiming that Hillary Clinton was not the target of the FBI probe into her use of a private server while she was Secretary of State.

"Below not helpful," Strzok wrote. "Certainly the WH is going to do whatever it wants, but there is a line they need to hold with regard to the appearance of non-interference."

We also learned in May that Peter Strzok went on a secret trip to London in the summer of 2016 to meet with Australian ambassador, Alexander Downer, to describe his meeting with Trump campaign advisor, George Papadopoulos. The FBI kept details of the operation secret from most of the DOJ - with "only about five Justice Department officials" aware of the full scope of the case.

It was an assignment so secretive that Peter Strzok giddily texted his side piece about it on an unsecured line. It's also weird for NYT to characterize the meeting as "not yet reported" seeing as how Strzok's texts about it have been out for months. https://t.co/lbvTZksLJr pic.twitter.com/QSA7TedpTM — Sean Davis (@seanmdav) May 16, 2018

Fearful of leaks, they kept details from political appointees across the street at the Justice Department. Peter Strzok, a senior F.B.I. agent, explained in a text that Justice Department officials would find it too “tasty” to resist sharing. “I’m not worried about our side,” he wrote. -NYT