Olympic 50m freestyle champion Cesar Cielo has refused to talk about the warning he received after testing positive for a banned substance last year and was forced to rely on a CAS appeal to get to his blocks for the defence of two world titles in Shanghai a year ago.

The world record holder over 50m and 100m freestyle was asked about the doping case in which he and three training partners were let off with a warning after judges accepted that a caffeine-based food supplement they had taken could have been cross-contaminated with a banned diuretic at the laboratory that made the product they had intended to take.

"I am here to swim fast, nothing more to talk about," said Cielo, speaking at Brazil's training camp at Crystal Palace in South London. "My main goal is to represent my country in the best way possible and to get a gold medal in the 50 and try my best in the 100."

He was happier to talk about the weather than a troubling 2011: Britain has had one of its worst summers on record but Cielo said with a smile: "Sao Paulo is pretty much like this too. It is grey most of the time, you know I was expecting a little more sun."

His world records from 2009, of 20.91 over 50m and 46.91 over 100m, were irrelevant, he believed. He did not mention the buoy of shiny suits banned since January 1, 2010 but focussed on what has long been a reality in world-class swimming.

"It does not stand for much," he said. "In the Olympics everything goes back to square one. The world champion or the world record holder or the ninth last year are fighting for the same medal and you have got to go there like it was the first time."

When Cielo took gold in the 50m and shared bronze in the 100m four years ago, James I and James II of Australia, Magnussen the Missile and Roberts the Rocket, were still dreaming of making their first Aussie team. In Shanghai last year, Magnussen shot to prominence when he led the Australian 4x100m free relay to victory with the swiftest 100m ever seen in textile suit, and followed up with a 47.63 blast for the solo 100m world crown. 

In March this year, he moved the game on to 47.10, his margin of advantage over the rest of the world worthy of his inclusion in a rare club of sprinters who stood head and shoulders above their peers: the likes of Kahanamoku, Weissmuller and on to Montgomery, Biondi and Van Den Hoogenband. 

History also points to Popov, who rarely put much water between his last stroke and that of the next man home but had the Midas Touch like no others in history. Magnussen's career is in its infancy, his ambition in London not only to become the first Australian since Mike Wenden in 1968 to win the blue ribband crown but harness that to a status of "fastest swimmer ever" (over 100m, at least).

Teammate Roberts is closest, on 47.63 at Aussie trials. Add in Eamon Sullivan and Matt Targett and you have the favourite-for-gold quartet in the 4x100m freestyle. 

In the 50m solo event, Cielo remains the man to beat, his advantage in the dash comparable to that enjoyed by the Aussie quartet.

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