By Rob Dugdale
BBC Sport in Pardubice
Deng scored 21 points in GB's victory
Great Britain qualified for the European Championship finals for the first time in 28 years after beating the Czech Republic 67-63 in Pardubice.
Luol Deng scored 21 points and Nate Reinking had 20. GB scored the last seven points of the match - all from free throws, to seal their victory.
Neither team had a double-digit lead in a close, tense encounter.
Jiri Welsch threatened to win the game for the Czechs but missed his last shot of the game, with three seconds left.
Welsch, who has NBA experience, had 28 points in the match but it wasn't enough to stop Great Britain clinching the away win they needed to qualify for the finals in Poland next year.
Earlier, Israel had beaten Bosnia 88-74 in Tel-Aviv, giving GB the chance to close out qualification with a fourth win in a row and the first away win in Group D.
This was two teams playing for everything
GB captain Andrew Sullivan
"I wouldn't say it was a nervous game exactly," said Pops Mensah-Bonsu, who completed the win with two free throws 1.5 seconds from time and finished with nine points and 12 rebounds.
"It was two teams who came out to play and couldn't afford to lose. You saw the way Jiri came out scoring tonight."
Deng and Welsch almost traded baskets in the first half and both had 14 points at the interval.
In the third quarter, 10 points from Reinking kept Great Britain ticking over and narrowly in front.
The Czechs came good in the fourth quarter, when threes from Welsch and Tomas Satoransky gave them a 63-60 lead with 2:35 remaining.
But that proved to be their last score of the night as Mensah-Bonsu, Deng, Richard Midgley and Mensah-Bonsu again held their nerve from the free throw line.
"We knew it would be a half-court game and ugly for the most part," said GB captain Andrew Sullivan after the game. "This was two teams playing for everything - us to qualify and the Czechs just to stay alive in the group.
"Fortunately we were able to make enough plays to get the win - and now we're qualified."