Marathon: Radcliffe faces the most gruelling course of all

It was a wail - a far from usual sound for Paula Radcliffe. But as she stood, distracted, in the mixed zone in Sydney four years ago, bereft of tangible reward for leading the Olympic 10,000 metres for 20 of its 26 laps, her habitual poise had vanished.

It was a wail - a far from usual sound for Paula Radcliffe. But as she stood, distracted, in the mixed zone in Sydney four years ago, bereft of tangible reward for leading the Olympic 10,000 metres for 20 of its 26 laps, her habitual poise had vanished.

"No one remembers who was fourth!" she cried. And she has never forgotten.

As she toes the line in Marathon tomorrow evening she will be on the brink of a race that will define her career. Radcliffe has been travelling towards this moment since she began racing as an eight-year-old, maturing as a competitor to the point where she now stands clear as the best female marathon runner in the world.

Amid the welter of accompanying statistics, this is perhaps the most significant: three minutes, 22 seconds. It is the gap between the 30-year-old British athlete and the fastest of her rivals.

But Radcliffe's stupendous world record of 2hr 15min 25sec was set on the relatively easy route from Greenwich to The Mall, where she has earned two of her three marathon victories so far, the other success coming on the flat highways of Chicago.

Her task tomorrow will be to translate that superiority on a brutal course in savage heat. If there is any lingering trace of the calf injury which hindered her preparations last month - and that remains a possibility even though team officials have dismissed rumours - then this is a challenge which will surely find any such weakness out.

Big city marathons, and even major championships, are simply not run on the kind of terrain that the historic 26-miles-and-385-yard route to the Panathinaiko Stadium presents.

As team coach here for the UK Athletics endurance runners, Alan Storey has made it his business to appraise the circumstances of the race very closely.

"The course starts fairly flat, and then there's a gradual rise between six and 10 miles," he said. "After that there is an eight-mile climb where you rise around 650 feet. We would call that a pretty big hill in the UK. The top of the hill comes in the suburb of Stavros - 770 feet above sea level. You then drop just as quickly towards the stadium, although the finish is still 200 feet higher than the start.

"It will be a question of seeing which runners will be in good enough shape at that point to use the hill to their advantage. After 20 miles of uphill running in the heat, some athletes will find their legs stiffening up."

Even at six o'clock in the evening, when the marathon starts, the sun will be unrelenting and the temperature will be over 85 degrees. While the whole course will be on a newly-laid road, there will be no cover, save perhaps in the latter part of the race when buildings may offer some shade.

Nor will the wind offer much assistance, Storey explains, as it is likely to come from the north. "That means in the early part of the race you will be running in effectively still conditions, at the same speed as the wind. There will be no air flow across the surface of the skin, so the heat of the body will stay the same. Ideally you want to be running in a crosswind where the heat is taken away without slowing you down."

Radcliffe, of course, is not averse to running up the odd hill. The bulk of her training takes place at high altitude, either in Albuquerque, in New Mexico, or Font Romeu, in the French Pyrenees, where she and her husband Gary Lough own an apartment. More recently she has acclimatised to the heat by training at a secret location in southern Spain.

Tactically, she has two clear possibilities - either to take the lead from the start, as she prefers to do in her city marathons, or to hang around until the runners approach the final stages of the climb to Stavros before breaking free. Should she decide on the former option, which suits her temperamentally, she will have to be very sure she does not, as she would say, "overcook" it.

The presence of a strong trio of Japanese athletes - Mizuki Noguchi, Reiko Tosa and Naoko Sakamoto - will ensure that she has little margin for error as they are going to be running as a team in order to try and stay in touch with the Briton they respect so much.

Noguchi is marginally the fastest of the Japanese trio, with a best of 2:21.18, but Radcliffe's most likely rivals are the Kenyan pair of Catherine Ndereba, the second fastest woman in history with 2:18.47, and the winner of this year's London marathon in the Briton's absence, Margaret Okayo, who has run 2:20.43.

Romania's Lidia Simon has first hand knowledge of the demands of the route which, according to the ancient historian Herodotus, was taken by Pheidippides in 490BC to bring news of the Greek triumph over the Persians. Seven years ago she finished with shoes full of blood and suffering from dehydration after claiming the bronze medal in the World Championships.

Others whom Radcliffe will be aware of include the Chinese trio of Helan Li, Shujing Zhang and Chunxiu Zhou. Given the Chinese record at these Games as they build towards the 2008 Olympics in Beijing, it would be unwise to rule them out.

Storey, however, believes that the majority of the field are simply too far behind Radcliffe in competitive terms to have a realistic chance. "You wouldn't expect anyone to make a five-minute jump just because of the weather conditions," he said. "It's very unlikely that there will be a surprise winner."

Such things have happened. At the 1999 World Championship in Seville, the marathon went to a runner from the People's Republic of Korea who has not competed since.

The crucial factor in tomorrow's result, however, is the state of mind in which Radcliffe approaches the biggest race of her career, as she attempts to maintain the family tradition of Olympic success established by her great-aunt, Charlotte Radcliffe, who earned a silver medal in the pool in the 4x100m freestyle relay at the 1920 Games.

If she does have any concerns about lingering, niggling injuries it will inevitably affect the way she sets about a task that has, thus far, always proved grindingly simple. But her startling success on the roads thus far will be working to her advantage, both in inhibiting her rivals, and inspiring her.

"I'm a stronger person now than I was in Sydney," she says. "I have more confidence - that is the big factor the marathon has brought me. And as an athlete, I feel there is unfinished business."