Paula Radcliffe today ended all the speculation about her fitness by declaring she will definitely run in the Olympic marathon here.

But Britain's greatest runner admitted she had been living through a "nightmare" with injury and was not prepared to make any rash predictions about winning the one gold medal which would crown her glittering career.

Radcliffe provided Team GB with their best possible boost with the Games just four days away when she arrived at the preparation camp in Macau to announce: "There's no decision to be made. I'm running unless the leg breaks down." The 34-year-old insisted she felt good but admitted that when she lines up in Tiananmen Square a week on Sunday in her fourth attempt to win that elusive Olympic medal, she won't be able to gauge what shape she is in to challenge in Beijing's suffocating heat and smog.

Radcliffe, who had looked destined to miss out after a stress fracture in her left thigh was diagnosed in May but has made remarkable progress, explained: "The aim's always been to start the race. The whole thing has been a race against time and a nightmare from when it was diagnosed but I'm getting more and more confident because every day, you run more on it and it gets stronger."

Radcliffe has done as much rehabilitation in the swimming pool and on the treadmill as running.

"I feel happier even to be at this stage but it's impossible to judge shape. I know I'm in good enough shape to be on the start line but I'm probably not in 2:12 shape," said the woman whose world record at the distance stands at 2hr 15.25sec. "But I think if you put yourself on the start line, you're in with a chance."

Husband and coach Gary Lough said he and Radcliffe would make the final verdict on participation, even though UK Athletics had insisted it would a joint decision.

Radcliffe's fairly downbeat assessment echoes that of senior UK Athletics officials who believe, privately, that it would now take a miracle for her to gain the ultimate redemption after the drama of the Athens Games when, after suffering a leg injury and a severe stomach complaint, she was forced to pull out in distress in the searing heat a few miles from the finish.