Douglas qualified as a solicitor in 1990. He worked in private practice for seven years in immigration law and crime before joining Westminster City Council in 1997 to specialise in children's work.

He was one of the founding partners of the firm. He has been a member of the Children Panel since 1998 and acts for children in public proceedings and Guardians in Rule 9.5 matters. He represents Westminster City Council and other applicant Local Authorities as well as parents in public law proceedings.