The two athletes undoubtedly ended the Games as its stars, and it’s hard to see how Phelps’s exploits can ever be exceeded never mind equalled.
The 23-year-old from Baltimore already had six gold medals under his belt after a dramatic Olympic debut in Athens in 2004, and now his sights were set on the record of most golds in a single Olympics belonging to fellow American Mark Spitz.
Everything had to fit into place if Phelps was to achieve his goal of eclipsing Spitz’s mark of seven victories.
He undoubtedly had the ability to win the individual events but so much can go wrong in the relays, their unpredictability being their main appeal and Phelps would ultimately depend on his team-mates for three of his gold medals.
No incident highlighted the frailty of relay success more than at the 2007 world championships when the weary Phelps was rested for a heat, only for a false start by team-mate Ian Crocker to end his hopes of eight gold medals in Melbourne.
Phelps started as he meant to go on in his first gold event in Beijing, the 400m individual medley, when he shaved a second off his own world record and finished over two seconds clear of Laszlo Czeh in second.
Golds and world records followed in the 200m freestyle, 200m butterfly, 200m individual medleywhile he and his team mates clinched gold with some ease in the 4x200m freestyle relay and the100m medley relay.
Landmarks were being broken everywhere.
As he took gold in the 200m freestyle he joined athletes Carl Lewis and Paavo Nurmi, gymnast Larisa Latynina and Spitz on the record of nine Olympic golds. He passed them with his win in the200m butterfly.
It was not all plain sailing though. In two events Phelps’s hopes of eight golds looked dead and buried.
In the men’s 4x100m freestyle relay, Phelps’s team-mate Jason Lezak started the final leg some 0.6secs behind individual gold medallist Alain Bernard of France but somehow managed to scramble the Americans home in world record time.
Phelps’s sinew-stretching celebration at the end of that race became one of the most iconic moments of the Games.
The second time his ambitions appeared thwarted was in the 100m butterfly, when Serbian Milorad Cavic appeared to have the American beaten only for Phelps to touch home first with one galumphing final lunge to snatch victory by one hundredth of a second.
So stunned were the Serbian contingent at the setback that they contested the result, but it rightly stood. The TV replays showed that Phelps had touched home first by a whisker.
Phelps finished 2008 with eight golds to his name from Beijing, 14 overall - five more than any other Olympian in the history of the Games.