London (AFP) - South African Wayde van Niekerk sailed through heats of the 400m to get his ambitious bid for a 200m-400m double off to a good start at the IAAF World Championships on Saturday.
Nery Brenes shot out in the heat and led coming into the home straight, but van Niekerk coasted through with a glance to the lanes outside him to win in 45.27 seconds.
Much is expected of van Niekerk, the world and Olympic champion who smashed American Michael Johnson's world 400m record when winning gold in Rio last summer in 43.03sec.
Even Usain Bolt has pegged the 25-year-old South African as his most likely successor as the athlete capable of dominating the track after the Jamaican sprint star's exit from athletics after these world championships.
But van Niekerk, seeking a first double since Johnson achieved the feat at the 1995 worlds in Gothenburg and a year later at the Atlanta Olympics, will be up against it in what looks like one of the highest quality fields in all events in London.
US college runner Fred Kerley, 22, and Steven Gardiner of the Bahamas, 21, won their respective heats in 44.92sec and 44.75sec.
"I'm in shape and you've got to give it your all each and every day," said Kerley. "It was a nice performance in my first world championships race and I'm excited to get into the semi-finals."
But van Niekerk's main rivals, in the absence through injury of Grenada's Kirani James, could likely be from Botswana's stable of runners.
Elder statesman Isaac Makwala, 30, raced to a convincing 44.56sec victory in his heat - the quickest time - ahead of American veteran Lashawn Merritt, former world and Olympic one-lap champion who has six successive global 4x400m relay titles to his name.
Makwala last month became the first man to run a sub-20sec 200m and sub-44sec 400m on the same day, clocking 19.77sec and 43.92sec respectively in Madrid.
A week later he ran van Niekerk all the way to the line at the IAAF Diamond League in Monaco, clocking 43.84sec before announcing that he - like the South African - would also be seeking a 200-400m double in London.
"Everything is okay," said Makwala. "I know I am ready, but at the same time I take everything step by step. If I qualify for the final then that is my focus, but until then step by step, always.
"Wayde van Niekerk is my brother. We want to conquer the world together and make the final for Africa. He is so friendly and a lovely guy."
Merritt added: "I haven't had the best season. I've been dealing with little bits, but I'm here now, and when I line up, I give it my all. I'm wishing for the best out of these championships.
"My motivation is that I didn't get a chance to run here in 2012 because I was hurt, and I have some things going on with my body at the moment that I have to mentally overcome. But I'm a warrior and I'll line up and give it everything."
Makwala's 20-year-old teammate Baboloki Thebe, who ran a personal best of 44.02sec at last month's IAAF Diamond League meeting in Lausanne, won his heat easily in 44.82sec in a warning shot to van Niekerk that he will not have it all his own way come Sunday's semi-finals ahead of Tuesday's final.