Cameron Norrie secured a stunning win over Rafael Nadal as Great Britain claimed an early 2-0 lead in their United Cup Group D contest with Spain in Sydney.
Tim Henman's team opened proceedings with a 3-2 win over Australia in their first series before Norrie and Katie Swan began day three against Nadal and Nuria Parrizas-Diaz in their respective singles contests.
In the day's maiden match, Norrie claimed one of the biggest victories of his career so far, recovering from a set down to defeat the 22-time Grand Slam winner 3-6 6-3 6-4.
After breaking Nadal's serve in the sixth game of the second set, Norrie brought up two set points on Nadal's serve, although he failed to convert either of them before levelling the match in the next game.
Nadal - who appeared to be struggling with his long-standing foot issue - was broken again in game five of the third set, and Norrie beat away three break points for the Spaniard en route to victory in two hours and 44 minutes.
Swan successfully made it two for two on Saturday after launching her own inspired comeback, defeating Parrizas-Diaz 3-6 6-1 6-2, despite finding herself a set and a break down.
Parrizas-Diaz won five of the opening six games of the match before breaking straight away in the second, but a front-footed Swan came storming back to win a staggering eight games in a row.
Keeping up her relentless pressure in the third, Swan squandered five match points before converting her sixth, and Harriet Dart will open Sunday's matches against Paula Badosa.
Dan Evans then takes on Pablo Carreno Busta in the men's singles match, and the 32-year-old will subsequently join forces with Dart to face Nadal and Badosa in the final doubles encounter.
Ben Knapton
