The 37-year-old has high hopes of bettering the second-place finish in last year's marathon, and spent time training at altitude in Albuquerque, New Mexico. However, after she and husband Shigetoshi left there last Thursday and arrived in Denver, they found no flights to London because of the volcanic ash cloud.
They eventually flew to Lisbon, took a taxi to Madrid, drove to Le Touquet and then boarded a propeller plane to Shoreham on Wednesday evening.
The Oxford-born runner's preparations may have been severely disrupted, but she is determined to make an impact on Sunday.
"It was fantastic weather and fantastic scenery," she said. "If this had not happened, I would never have seen all the things I did, from Lisbon to Madrid, up to Paris, then down to Le Touquet and from Shoreham up to London.
"Some of it was gorgeous but we were just focused on trying to get to the next place, making sure we did not go wrong.
"Physically it was pretty exhausting, but on the positive side I was not really worrying about the race at all."