Willis obviously didn't need to run quicker than 41 sec for the last 300m:
An elated but relaxed Willis said he felt in control as he took the field apart in the final lap.
"I was making sure I saved a little bit, just to respond to any challenges," he said.
"Fortunately I was able to save a little bit and just to raise my arms for myself and my country and all the people who have supported me over the years have been really awesome."
Willis admitted to concern over his throat infection in the leadup, which brought on anxiety. He didn't start feeling better until Tuesday.
"It's been a pretty trying time for me the last two or three weeks, with highs and lows with my stress levels and anxieties," he said.
"It was a huge relief coming down that home straight, looking up at that big screen thinking, `wow, I've still got seven metres, when are these guys coming'."
He felt he had the race won with 50m remaining.
Willis didn't think his win had been tarnished by Mottram's fall.
He wasn't completely surprise that Mottram had fallen as the Australian was a runner who was used to longer distances and didn't like to run in a packed group.