The barnstorming left winger produced the match-winning try with 12th minutes remaining with Australia behind 37-36.
A wide shift from outside their own 22 to the left put Lancaster down the edge, he rounded Fiji’s defence to score untouched under the posts before a final penalty goal put the game out of Fiji’s reach.
Australia were made to work for the result after Fiji hit back at opportune times just as the Junior Wallabies looked like running away with the game.
