During a three-week visit to New York in April 1966, Barker became acutely aware of American consumer culture embodied in the Coca-Cola bottle. His friendships with Jim Dine, Roy Lichtenstein and Tom Wesselmann focussed his attention on pure Pop Art language. Barker cast his first Coke bottle immediately upon his return to London in May 1966. In 1968, Barker returned to the Coke bottle as a subject for two years, when he subjected it to numerous permutations: bottles in pairs or groups of three, with or without straws, upright and on their side, with caps on, off, in the process of being removed.
Barker’s newest Coke bottles, this time rendered in shiny enamel colours were inspired by his job as a youth at the Luton Vauxhall Car Factory. The enamel colours were sourced in the car industry.

Museums holding Barker's work include: Tate, London; British Museum, London; National Portrait Gallery, London; Staedtische Kunsthalle Mannheim, Museum für Moderne Kunst, Frankfurt; National Gallery of South Australia, Adelaide; The National Museum of Contemporary Art, Lisbon; The Hirshhorn Museum and Sculpture Garden, Washington, D.C.; Philadelphia Museum of Art, Philadelphia.