A controlled performance on the rings was followed by a vault which reproduced his fine display on the apparatus in qualifying, then a confident, skilful parallel bars routine.
When Keatings kept his cool on the high bar and landed safely, the crowd erupted - but everyone inside the arena faced an anxious wait for the last gymnasts to complete their routines.
"I'm ecstatic and relieved," said coach Hall. "It was very stressful but just fantastic.
"He was really cool, he did a superb job - all the years of hard work have paid off."
Uchimura, who mesmerised with the difficulty and standard to which he executed his performances throughout, refused to buckle under the pressure of taking to the high bar last in his quest for gold.
The Japanese star, one of the pre-event favourites to win, dispelled any hopes Keatings had of gold with a magical routine, improving on his silver medal behind China's Yang Wei at last year's Beijing Games.
Thomas, 20, would have been delighted to squeeze into the top 10 prior to the competition, but surpassed himself with a succession of impressive displays.
His superb dismount from the rings, unbelievable score of 15.800 on the vault, and elegant performance on the floor were highlights of a performance few could have predicted.
Thomas 'ecstatic' with World sixth
"It all came together in the end," he said. "On the first few pieces I was quite shaky, but I loved every minute of it. It was one of the best feelings I've ever had."
Ryazanov sealed the bronze with a similarly impressive display on the vault, and a beautiful floor routine to finish.
United States duo Timothy McNeill and Jonathan Horton will be disappointed with their performances, particularly Horton, who had a disastrous start on the floor, lost his way during his pommel horse routine, and fell on the high bar.
The World Championships are being held in London for the first time, and will return to the O2 Arena for the Olympic Games in three years' time.
The results obtained by Keatings and Thomas, with pommel horse specialist Louis Smith still to compete in his final on Saturday, suggest Britain will now be serious contenders for medals at London 2012.
Previously, Neil Thomas, who placed 16th for Britain at the 1994 World Championships, had the country's best result at an all-around final of this standard.
Becky Downie and Rebecca Wing go in the women's all-around final on Friday and, though neither are considered medal prospects, they may feel anything is possible having sampled Thursday's atmosphere.
On Sunday, Beth Tweddle will round off the British campaign at the Worlds in the final of the floor event.
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