Paula Radcliffe has decided not to race in the marathon at the World Championships in Berlin after testing her fitness in her first race for 10 months last weekend.
Radcliffe blazed to victory in the New York City half-marathon with a world-class performance after a long absence recovering from a foot operation.
She was delighted with her display but the world record holder believes she is still about three weeks away from the condition required to win the gold medal.
Radcliffe's recovery has been excellent but the New York outing confirmed fears she is not yet quite ready to compete 100 per cent over a full marathon.
"I am devastated that I wasn't able to be ready in time to represent Britain here in Berlin, especially having got so close in such a short time frame," Radcliffe said.
"However, after having the surgery to successfully put the years of injury behind me it is very important to me that I come back to racing often and winning at 100 per cent and continue strongly and successfully through to London 2012.
"It has been great to be here and to spend time with the team, which has performed so well so far, and I look forward to being part of it again in the near future.
"Running in New York was a necessary part of the process to ascertain my race fitness and, after speaking with my coaching and medical team, I knew I was sadly just not quite ready."
UKA head coach Charles van Commenee said: "To lose an athlete of Paula's calibre is disappointing to say the least.
"She won the World Championships in 2005 and a fit Paula would clearly be in contention to regain that title but she has taken that difficult decision and we have to respect that."