Wariner was never seriously challenged as he ran a personal best of 43.93sec, but the 23-year-old Welshman - whose awkward lane draw was a result of his qualification as one of the fastest losers - broke 45 seconds for the third time in four races, recording 44.93.
"Running sub-45 seconds from lane one was a massive experience for me," said the athlete who was flat on his back in hospital for most of March after a spinal injection went wrong. "I'm on the up and up. Just give me another year to put some work in."
Asked to comment on criticisms of Britain's performances here, he responded: "I can't speak for other people. I can only try my best, and that's what I've done. But I think these championships can be a great experience for young athletes like Nathan Douglas and Chris Tomlinson. They have got to have time to develop."
There was, however, a significant development in the medal prospects for Britain's sprint relay team today as the Americans dropped the baton in their semi-final.
There was a collective chuckle as the American's first changeover between Mardy Scales and Leonard Scott came to grief in the sprint relay semi-final. The team which, as ever, had all the individual talent to choose from, had managed once again to become less than the sum of its constituent parts. At the end of a very bad week, it was a piece of startling fortune for the Brits...
And it was a particularly poor moment for former 100m champion Maurice Greene, who was here purely for the relay and was left stranded on the fourth leg. He must now travel back to the States without having run a step in anger .
"Passing a stick isn't that complex, but we don't practise it enough," Greene said. "It's been a rainy vacation, I guess."
Britain - using three of the four men who secured Olympic gold last summer - are the second fastest qualifiers with 38.32sec behind Trinidad and Tobago, who clocked 38.28, and have a real medal chance.
As indeed does Paula Radcliffe as she sets out in pursuit of her first global title tomorrow afternoon in the marathon. Albeit that this is an event where favourites can rarely be seen as such. As Radcliffe knows only too well from last summer, too many things can go wrong.
But the 31-year-old must be praying that all her ill fortune came at once in Athens as she takes to the roads of Helsinki against a field where her one obvious rival is the woman from whom she took the world record, the defending champion, Catherine Ndereba of Kenya.
Having recovered from finishing a distant ninth in last Saturday's 10,000m final, Radcliffe said she had no niggles or injuries as she prepared for a race which could help to heal, if never erase, the scars of her double Olympic failure.
"Everything is in as good a shape as it could be at the moment," she said, adding that she felt no particular pressure as Britain's only realistic gold medal hope.
While the three Japanese runners who have also got an eye on the World Cup event incorporated into tomorrow's race have been training on the course for several months, Radcliffe was confident that she had already done enough to familiarise herself with the route.
"I'm aware that the Japanese have been preparing thoroughly, and they have been out training on the course," she said. "It's all about what works for each individual. I've never done that before any of my marathons. I probably only ran the last 300 metres in New York last year. It didn't do me any harm then and I don't think it will now.
"I've driven round the course in a car. I prefer to do that as I take it all in better that way. I think the course is nice, testing in places but nothing bad."
As last year, she has run three minutes faster than any of her opponents. And she says she is OK. And Helsinki has not been that hot recently.
Yelena Isinbayeva's victory in the pole vault was only slightly less surprising than her subsequent achievement of adding another centimetre to the landmark world record of 15.00m she set at Crystal Palace last month.
Christine Arron's hopes of winning the 200m gold faded to bronze as 19-year-old Allyson Felix came past her in the last 20 metres.Reuse content