Reginald Brown, chairman of Wilmer Cutler Pickering Hale and Dorr’s financial institutions group and head of the firm’s congressional investigations practice, has been retained by President Donald Trump’s former top campaign adviser Paul Manafort Jr., according to a source familiar with the matter.

Brown declined to comment when asked about his role representing Manafort, who on Friday said he was willing to appear before members of the House Intelligence Committee to put to rest questions about his alleged ties to Russia.