Deena Kastor finished 18th at the Virgin London Marathon. The 2006 winner had her preparations disrupted by the volanic ash travel backlog and overcame an arduous two-day journey from America via Paris.

The American marathon record holder crossed the line in 2:36:20, her slowest time for any marathon she had completed since taking up the event nine years ago.

"I felt terrible right from the start," said Kastor, 37, a bronze medallist at the 2004 Olympics. “I tucked in and just thought I needed to shake out travel and tightness. I felt very tight and stiff at the beginning of the race, and it never shook out."

"I was cramping and tight in my back and my legs from probably about mile six. Then at that point thinking like that felt like the half-way point was pretty discouraging. I looked up at the (lead) truck at one point when the pack was leaving me and I saw that their third mile was 5:05. And I said, 'OK, I'll just stay steady at this pace and maybe some people would start to fall off the pack and I can start reeling people back in.'"

"I just didn't want to drop out of another race," Kastor said. "I dropped out of New York before, I was forced to drop out of Beijing, and I don't want to ever have to do that unless it's dire circumstances. If I could keep moving forward, I wanted to commit to that finish line. I put too much work into this race to not get there."

Kastor hopes for better luck at the ING New York City Marathon in November.