The 20-year-old world champion’s 47.10 seconds swim in Adelaide improved on his personal best of 47.49 set in Shanghai last year and was just 0.19 shy of Cesar Cielo’s world record of 46.91 set at the 2009 world championships.
Only Cielo, Frenchman Alain Bernard (46.94) and Australian Eamon Sullivan (47.05) have swum faster.
“Brace yourselves,” Magnussen said in a poolside interview after his lightning swim from lane four beat runner-up James Roberts by more than half a second.
“I gave it everything,” he later told reporters.
“I backed myself tonight and really went after it and I really felt it in that last 10 meters.
“I feel pretty confident after that swim, I’m certainly not going to rest on my laurels.
“I’m going to be doing everything within my power to break that world record because I do want to be considered the fastest man in history.”
Magnussen, nicknamed “the Missile” Down Under, said he had been told that he would need to make the 50 meters split in 22.80 seconds to have a chance of breaking the record and the spiky-haired swimmer did just that, rocketing to the wall in 22.68.
With the packed crowd at the 3,000-seat South Australia Aquatic and Leisure roaring him home, Magnussen charged back to the wall but pain filled his arms in the last 10 meters and the record went begging.
The swimmer from the small coastal town of Port Macquarie dismissed the notion that he had gone out too hard to beat Cielo’s mark, which was set in a now-banned swimsuit.
“I’ve been working a lot on my speed and my speeds in training sort of indicated that I can back up those sort of front ends and you can never prepare yourself for the pain you feel in the last 10 meters,” he said.
Roberts, who shares the same age and the same birthday of April 11 with Magnussen, pushed the world champion all the way and matched his mark of 47.63 seconds set in the final of Shanghai.
“That was probably the best thing that could have happened to me tonight to have James sort of push me the whole way,” added Magnussen, who swam in a knee-length suit.
“I was expecting to see clear water on the way home and I looked across and saw him it was like — (expression of shock).”
“I’m really happy for him to do that tonight. We’ve been racing each other for a long time and hopefully now we’ll be at London together in that relay team, giving it to the rest of the world.
“If the Olympics were going to be tomorrow you would have to say that (our) relay team is pretty bullet-proof, but you know, the rest of the world can try to catch us.”
Magnussen, along with Sullivan, Matthew Abood and Matt Targett won the 4x100 freestyle relay gold in Shanghai.
Abood finished a heartbreaking seventh to be outside the top six that would be considered for selection for the relay team in London but it was a red-letter day for Roberts who missed out on gold at Shanghai.
“It was a little bit of a shock to see how far under 48 (seconds) I went but it’s a great feeling,” Roberts said.
“I was that person (who missed out) at world championships. I did the heat swim and unfortunately they sat me out of the final to go with experience but that paid off and we ended up winning the gold medal.”
Twice-Olympic medley relay champion Jessicah Schipper won the 200 butterfly to qualify for her third Olympics ahead of Samantha Hamill who took the second individual berth as runner-up.
Olympic silver medallist Brenton Rickard won his fifth 200 breaststroke title, while triple Olympic champion Libby Trickett qualified fifth into Tuesday’s final of the women’s 100 freestyle.
Trickett was disappointed after failing to finish in the top two of the 100 butterfly title earlier in the trials, putting paid to her Olympic title defense, but can secure a berth to London if she finishes in the top six of the 100 freestyle.
