Yang, who obliterated Grant Hackett's decade-old 1500m record at last year's World Championships in Shanghai, won the Olympic qualifier at a leisurely 3min 42.31sec, some two seconds off his own national record.

He said: "I can't break the record every time, it's beyond imagination. I think the result today is good and I'm happy with it."

The 20-year-old, who also seized the world 800m title last year to become a leading Olympic prospect, said he was reaping the benefits from his training camp abroad and hoped for a faultless Games.

"I am clear about my level in the world and for me, the most important thing is to find problems and keep improving my results," he added. "I hope I can have a perfect performance at the London Games."

However, Beijing silver-medallist Zhang Lin placed only fourth and well outside the Olympic qualifying time of 3:48.92, endangering his bid to reach London.

He said: "I trained well and prepared well and I don't know why the result is so poor. It's hard to accept, but I have to."

China has closed the gap on the traditional swimming powers and looks set to make waves in London after finishing second behind the United States in the World Championships medal table last year.