Steve Bannon, the Trump administration’s former chief strategist, was interviewed by special counsel Robert Mueller over multiple days this week, NBC News reported Thursday, citing two unnamed sources familiar with the proceedings.

Bannon served as the Trump campaign’s chief executive from August 2016 through the end of the campaign, and was in Trump’s ear until he left his White House post in August 2017, making him a valuable interview for Mueller’s investigators.

NBC News reported that Bannon spent “some 20 hours in conversations with the team led by Mueller.”

Bannon returned to his job leading the far-right outlet Breitbart News after leaving the White House, only to leave that role early this year after losing favor in Trump’s circles for criticizing the President’s son in Michael Wolff’s book “Fire and Fury: Inside the Trump White House.”

NBC News also noted that Bannon had appeared before the House Intelligence Committee again on Thursday to answer Russia-related questions. Members of both parties in that committee have openly considered sanctioning Bannon for refusing to answer their questions. CNN reported Thursday that Bannon claimed to have been instructed by the White House to invoke executive privilege in response to a broad range of questions.

“The only questions he would answer were questions that had been scripted, literally scripted for him by the White House,” NBC News quoted the committee’s ranking member, Rep. Adam Schiff (D-CA), as saying Thursday. “Whenever we sought to probe anything beyond the four corners of the specific wording of the question, he refused to answer. That’s not how executive privilege works.”