As discussed earlier, one of the major concerns about Steve Bannon's closed-door testimony before the House Intelligence Committee on Tuesday, is that he refused to discuss any of the things that were of biggest interest to his interrogators.

As we reported, Bannon invoked executive privilege during his meeting to avoid sharing details about his time in the Trump administration, where he served as chief strategist, or during the presidential transition. In fact, Bannon reportedly stopped answering questions once his lawyers had alerted the White House that the scope of the House panel's questions would be expanded to include his time in the White House.

However, as Axios reports, Bannon made one conspicuous slip up: he admitted that he'd had conversations with Reince Priebus, Sean Spicer and legal spokesman Mark Corallo about Don Junior's meeting with the Russians in Trump Tower in June 2016. As a reminder, this is the meeting that Bannon allegedly told Michael Wolff was "treasonous", and led to the violent fallout in relations between Trump and Bannon.

This matters because the meeting — and the subsequent drafting of an allegedly misleading statement on Air Force One — has become one of the most important focal points of the Russia investigations, both on Capitol Hill and within Robert Mueller's team, as it provides the closest thing that exists to evidence that the Trump campaign was willing to entertain collusion with Russians, according to Axios' Jonathan Swan.

Bannon immediately realized he'd slipped up and disclosed conversations he wasn't supposed to discuss, because they happened while he was chief strategist in the White House. Throughout the rest of the session, committee members — in particular Republican Trey Gowdy and Democrat Adam Schiff — hammered Bannon over the fact that he'd mentioned those conversations but refused to discuss anything else about his time in the White House.

This is also why the pressure on Bannon to disclose all he knows will only grow, and also why Mueller will be especially interested in what he has to say.

Aside from this once incident, Axios reports the following "insider-the-room" moments: