Despite being drawn in the tight inside lane, the world champion was relatively untroubled and qualified fourth fastest clocking 48.98 seconds.
And the 26-year-old admitted he still has something left in the tank as he bids to beat world No.1 Javier Culson who qualified fastest overall with a time of 48.33.
“It’s what we do for a living, trying to focus, and I guess I’m not usually that focused in the heats anyway,” said Greene, who is the captain of the British athletics team.
“The semi-finals will be different and I have to get my head down and really concentrate on what I have to do.
“I try not to be on it too much in the heats so the semi-finals are when it really starts for me.
“I don’t usually run the inside lanes very often but it was just a little bit tight. I knew I was a little bit better than the other guys so I shouldn’t have too many problems.
“As I walked out to the 300m mark to be introduced there was a massive cheer went up when people saw me.
“It was a fantastic atmosphere, we can hear it from the warm up track and it’s really inspiring.”
Meanwhile Alex Smith’s best throw of 74.71m was just good enough to scrape into the men’s hammer final while Stuart Stokes finished 12th in his heat of the 3000m steeplechase.
- Javier Culson