Olive Loughnane is quite happy to let her claim the limelight. The athletes have trained together for most of their careers they were involved in the group that established itself in Cork, where Gillian worked as a teacher after graduating from UCC, and Olive still works in the CSO. Robert Heffernan from Togher is another world-class race walker.
But yesterday Loughnane insisted she was quite content to go into the race in the shadow of her training partner, confident that she will not be too far away and she never is.
O'Sullivan goes into those championships as a very definite medal prospect. She holds indoor and outdoor world records and, domestically, holds every women's walking record in the books.
Since 1999, when she finished 32nd in the world championships in Seville, she has knocked more than nine minutes off her time. After launching her campaign with a big win in Tijuana, she goes into tomorrow's race as the leader of the Grand Prix series, which has a prize fund of $20,000, and it will take a world record from someone else to take that away from her.
Her success is the result of her professionalism, and her preparations for these championships could not have been more precise. Even the lead-up to the championships has been carefully planned.
She based herself in Annecy, where conditions were ideal for training, and 30 degrees of heat prepared her for what she can expect here tomorrow.
No matter what happens this will go down as a very successful season two victories and one second out of five races but she is a winner who wants to win.
"It would be fantastic to win and hopefully everything will go well," she said. "But even outside of that I've had a real good year, so at least I can be proud of that. But the win would be the icing on the cake."
She finished 10th at the Olympics in Sydney and fourth at the European Championships in Munich last year, when she was robbed of the bronze medal inside the last half-mile.
There were those who held that Elrica Alfrida of Italy could not have legally overtaken her with so much ground to make up.
"I'm still pleased with my own performance that day because it was a big jump forward at the time," she said. "It gave me the motivation to move on and now I only hope I can go one better here."
She realises the pressure is on her, going into the race as one of the favourites, but she uses it in a positive fashion.
"Every now and again you think about it and different things go through your head like the worst scenario that I will be disqualified, and the best that I will win a medal. But even if I have an off-day or things do not go to plan, I feel I can finish in the top five or six anyway."
Olive Loughnane realises that there will be pressure on her training partner going into the race but insisted yesterday that she can cope with it.
"She is really in superb shape," she said. "She is a very experienced athlete these days. But it is a really tough race. The two Russians are going very well and so is the Italian."
Olive was the best-placed Irish athlete at the last World Championships in Edmonton, finishing 13th. She was 13th again in the European Championships last year, and now she wants to break through that barrier.
She knocked more than two minutes off her previous best performance with a 1:30:27 in Russia this year, and she knocked all of 42 seconds off her best when winning the 5,000m walk at the national championships a couple of weeks ago.
Almost all of her family are here in support, including her husband Martin Corkery from Ballavourney, who played junior football for Cork, and her younger sister Ann, who won a silver medal at this year's world youth championships in Canada.
Karen Shinkins also has an early morning start, for the heats of the women's 400m. After early season frustrations due to injury, she hit form at precisely the right time.
"I was a bit worried a couple of weeks ago. I was not sure how the season was going to go. In fact I was kind of half thinking of calling it a season," she admitted, after retaining her national title in style. "I knew physically I was in good shape, but I had foot problems. I had a good coach and a good family around me and we decided to take a break from competition, get some treatment.
"I am back competing again, everything is clicking in and the times are coming down, so my form came back pretty quickly. I am excited about racing again, and feeling good."