Understrength Australia have lost their first tie of the United Cup after Ajla Tomljanovic's injury replacement Maddison Inglis became the third local to fall to their Great Britain rival in straight sets.
With Harriet Dart's 6-4 6-4 defeat of Inglis at Ken Rosewall Arena, Great Britain built an unassailable 3-0 lead before the mixed doubles and second-seed men's singles matches were played at the new team tournament.
When Tomljanovic tweaked her left knee on match day, world No.80 Inglis became the second Australian called in at the last minute after Alex de Minaur replaced Nick Kyrgios as Australia's top men's seed on Thursday.
But unlike de Minaur, Inglis had not been preparing to play in the tournament because Zoe Hives was appointed Australia's second women's seed.
Inglis traded blows with world No.98 Dart early but errors soon began to creep into the Australian's game and her rival took advantage.
Dart broke Inglis midway through the first set to take a 3-2 lead and threatened to do the same with her next chance, until Inglis clawed back and won the game.
Dart's backhand was a handful for Inglis, who blew two chances to break her opponent early in the second set and conceded her second break point in the following game.
The momentum finally appeared with Inglis when she broke Dart to lead the second set 4-3.
But the Australian made two double faults in the next game, giving her rival the chance to serve for the match, and the tie.
The precise Dart made no mistake, polishing her rival off in 92 minutes.
The injured Tomljanovic wore a bandage on her knee as she took her place with the Australian team at Ken Rosewall Arena.
She did not limp as she lined up for the national anthems and Tennis Australia remains hopeful she will be fit to face Spain's Paula Badosa on Tuesday afternoon.
Later on Friday night, Australian world No.107 Jason Kubler will be out to claim his first win from three matches against Dan Evans, who is ranked No.27 in the world.
In the last match of the tie, Australian captain Sam Stosur is teaming up with doubles specialist John Peers to face Evans and Dart in the mixed doubles.