Robert Mueller arrived on Capitol Hill on Wednesday to begin a marathon day of testifying before two House panels about the report on his two-year investigation into Russian interference in the 2016 presidential election.

He’ll appear first at 8:30 a.m. before the House Judiciary Committee, where he’s expected to be grilled about whether President Trump tried to obstruct his investigation.

The former special counsel will then appear before the House Intelligence Committee to answer questions about whether the Trump campaign colluded with the Russians during the election.

Mueller’s testimony will be the first time he has spoken about his investigation since May, when he announced that the probe had been completed and that he had no intention of testifying, noting that “the report is my testimony.”

“I do not believe it is appropriate for me to speak further about the investigation or to comment on the actions of the Justice Department or Congress,” he said.