Backley's late flourish, which was enough to defeat all but the surprise South African winner Marius Corbett, had the unfortunate side-effect of knocking his friend and training partner, Mick Hill, out of the bronze medal position. "I'm as sick as a flock of parrots," Hill said.
Britain's trio of 400 metres runners also experienced that let-down feeling after failing to gain a medal in a final won, as expected, by the defending champion, Michael Johnson.
Mark Richardson ran a personal best of 44.47sec in fourth place, with Iwan Thomas dropping back to sixth in 44.52 after a fast start and Jamie Baulch finishing last in 45.22.
Backley, who had begun the evening in search of the global gold which he said he needed to round off his achievements in his event, looked for most of the evening as if he would come away empty-handed. His first throw, on which he had pinned such hope, was only 82.94m. His face said everything about his disappointment. Last summer in Atlanta a big opening effort had been enough to secure silver, as only Jan Zelezny managed to beat it.
Zelezny also, to general amazement, came away with nothing, no-throwing twice and then failing to make the cut of the final three throws with his only recorded effort of 82.04.
Hill put himself into the silver medal position early on with throws of 84.48 and 86.54. But the competition was ultimately won by a startling second-round throw of 88.40m by the 21-year-old student Corbett.
World junior champion in 1994, Corbett was injured last year and not regarded even within South Africa as a medal prospect. His winning distance was an improvement of 10 metres in the space of a season. His best up until 1996 was 77.98, a distance he threw in 1994. This year he had managed 83.90 at altitude.
Earlier this season, Zelezny invited Corbett to throw in a high school meeting at Stellenbosch. Zelezny thew over 94 metres to lead the world's standings this year. Perhaps something rubbed off on the student.
The atmosphere in the stadium was predictably partisan as the Greek thrower Kostas Gatzioudis sought to match the South African's prodigious effort. He managed 86.64, which proved enough to earn bronze and a rapturous reception.
Backley, who appeared to be getting increasingly disconsolate, earned his medal with a final effort of 86.80. From a competitive point of view it was one of his finest efforts. Whether he will regard it as a silver gained or a gold lost remains to be seen. "He did the business again," Hill said. "In the long run I'm sure he'll be disappointed, but he's actually highly delighted now because he almost ended up with nothing."
Backley had mixed feelings: "I was absolutely delighted to have stuffed the Greek with the last throw," he said. But he complained that the Greek officials had started his clock going before giving him his javelin on two of his six throws. "It made me mad and that doesn't suit me."
Hill showed his disappointment by flinging away his throwing belt after his last effort. Until Backley's intervention, he had seemed ready to earn another world bronze to go with the one he won in 1993 following the disqualification of the third-placed man for a doping offence.
Thomas, who like Richardson has been receiving treatment for a niggling injury behind his knee, made a characteristically brave attempt to keep in touch with the defending 400m champion, going off very fast.
As the field turned into the final straight, the fair hair of Thomas, who was in lane two, appeared for a heady moment to be level with Johnson, but he could not maintain his momentum. First the champion, then Davis Camoga, Uganda's Olympic bronze medallist, then Tyree Washington, America's new kid on the blocks, came past him. Johnson was timed at 44.12, with Camoga second in 44.37 and Washington third in 44.39.
"I maybe went too hard for 300 metres but I've lost a bit of fitness recently and I couldn't hang on," Thomas said. "At least I gave it 100 per cent. I missed almost 10 days of training prior to this so I maybe lost the edge. But I am proud of myself for showing the guts to go for it. I planned to catch Johnson. I thought I could hold him off, but it wasn't to be."
Richardson was dejected. "I ran a personal best. I ran a very good race. A PB should be satisfying, but at the moment it's disappointing. Coming fourth is probably the worst position to come. I really thought I could get a medal. I ran the best race I possibly could. Normally bronze is won in about 44.50. That shows what a tough standard it was."