Barker studied at the University of New South Wales, where he obtained a Bachelor of Commerce and a Bachelor of Laws. The university was established in 1949 as the New South Wales University of Technology and adopted its present name in 1958.
His legal studies at the university preceded his admission to the bar in New South Wales in 1979, the year the Sydney firm Freehill Hollingdale & Page formed its first national partnership with a Perth firm.
Barker's documented professional life centres on Freehill, Hollingdale & Page, a Sydney law firm in which he worked as a partner. The practice traced its Sydney origins to 1871, when a legal firm was founded in the city by Bernard Austin Freehill. In 1947 the Sydney practice took the name Freehill Hollingdale & Page and expanded under the direction of partner Brian Page, who guided it toward corporate and commercial work within Australia and internationally.
The firm's development during Barker's admission period reflected its move toward a national practice. In 1979 the Sydney firm signed an agreement with Muir Williams Nicholson & Co of Perth, creating what was described as Australia's first national law partnership. In 2000 the state partnerships merged into a single national partnership known as Freehills, and the firm was later known as Herbert Smith Freehills. Its headquarters were in the MLC Centre in Sydney.
