Phelps already has more gold medals than any other Olympian. In his long week at the Beijing Games, he has invited a debate on the possible measures to compare the greats. Is Phelps greater already than Carl Lewis, for instance? Do swimming and athletics even compare? Must he return a gold for four consecutive Olympics to count? Can he be compared to Mark Spitz even?

Susan Casey, a writer with Sports Illustrated who has interacted with Phelps and his support team before and during the Beijing Games, prefers to stay with swimming comparisons. Spitz and Phelps belong to different eras, she says. “Spitz can be called the Phelps of his era. But I don’t think Phelps is (just) the Spitz of this era.” The depth of competition today, she argues, just does not sustain easy comparisons with the 1970s: “Phelps is in totally uncharted waters.”

To convey his uniqueness, she reaches for just one adjective: “complete”. He’s got everything, she says, physically, physiologically and genetically. “He’s taken the raw material and done the work.” For instance, she explains, he is “fantastic” at competing. “On the blocks, they say it’s 90 per cent mental. He has the mental ability to win.”

But these world records? Is it some kind of a statement, this taking of each of the first six golds with a world record?

No, says Casey, that’s what it takes to win.