Leedham is rated as world class by GB's coach Tom Maher
Johannah Leedham hit three three-pointers in the final quarter to lead GB's women to a 57-49 win over Ukraine in their third European qualifier.
Leedham finished with 18 points and Natalie Stafford added 10 as GB joined Germany and Slovakia for a tie for first in Group D at the halfway stage.
Britain had a poor first half but took their first lead with a 10-2 start to the third quarter.
Leedham's heroics ignited a 17-4 start to the final quarter to seal the win.
GB shot poorly from all distances in the first half at Surrey Sports Park and missed 10 free throws in the first 25 minutes.
After trailing 21-25 at half-time, bench players Azania Stewart, Rose Anderson and Rachael Vanderwal added extra energy to the mix and the first lead came on a Julie Page free throw early in the second half.
Stafford ended the third quarter with a pair of thee-pointers to stretch the lead to 38-35 but it was Leedham's start to the final 10 minutes that decided the game.
In the space of a little over two minutes she hit a three, stole a ball and adeptly recovered it and appeared at the other end for another three-pointer, then swished another for a 47-37 GB lead.
"It was awesome," said Stewart. "I just kept screening her player to get her open - I thought 'she's on fire, let's just let her rip.'"
"It's either over-anxiety or taking it easy," said coach Tom Maher of the first half.
"Jo didn't play well but she saved us by knocking those threes in. But she's a much better talent than that."
GB travel to Slovakia for their next game, on Monday in Kosice. Coach Tom Maher knows that will be a tough game against the group's top seeds, who beat GB in Birmingham last weekend.
Elsewhere, GB's men's enjoyment of their day off would have been helped by the news that Hungary had beaten Macedonia, GB's main rivals for automatic qualification, 85-82.
That result takes some pressure off Chris Finch's team ahead of the trip to Skopje, where they face Macedonia on Monday in what could be the decisive game in the group.
GB squad: Rose Anderson (Central Oklahoma Uni, USA), Kim Butler (Panionios, Greece), Stefanie Collins (UWIC), Chantelle Handy (Marshall Uni, USA), Johannah Leedham (Franklin Pierce Uni, USA), Julie Page (Aix, France), Azania Stewart (Florida Uni, USA), Jeneya Wade-Frey (Tennessee-Chat Uni, USA), Joanna Claydon (Leeds), Natalie Stafford (Barking), Rachael Vanderwal (Limerick, Ireland), Lisa Hutchinson (Sheffield), Meagan Hoffman (UWIC).
Women's EuroBasket qualifiers/results:
14 August: GB 67-76 Slovakia
17 August: Germany 63-72 GB
20 August: GB 57-49 Ukraine
23 August: Slovakia v GB (Kosice)
26 August: GB v Germany (Liverpool Echo Arena)
29 August: Ukraine v GB (Dnipropetrovsk)