It's been a challenge, admitted race director Dave Bedford today, but despite six days of grounded flights and a cloud of volcanic ash throwing a shadow over the event, the 2010 Virgin London Marathon on Sunday will feature the highest quality elite fields in its 30-year history.

"We've had a bit of a challenging week," said Bedford as he explained the efforts that have been made to get world and Olympic champions, reigning title holders and record setters from all over the world to the British capital.

"Early in the week we thought we'd get some of our athletes in but certainly not all. It was only when the skies re-opened that we saw we could get them all here," said Bedford, who at one stage faced the prospect of staging a London Marathon missing some of top stars.

"I believe now we will have the best fields ever in the most challenging circumstances we have ever faced," he added. "As long as there are no negative effects on the athletes from all their travelling I expect to see some incredible performances on Sunday."

At a cost of nearly £150,000, taken from the event's contingency fund, the London Marathon chartered three private planes and called on "incredible support" from transport companies, Spanish race directors, athletes' agents and the British government to get its elite runners into London via Madrid from Africa, South America and eastern Europe.

Many of the top African and European marathons runners in the world will arrive at London's City airport from Spain at 17.30 this afternoon while others have eventually been able to make delayed journeys from USA, Japan and China in time for Sunday's race.

"I don't think we've ever hired a jet before," said Bedford. "But in the end I think it was pretty good value for money. You can't put on an event without a contingency fund and the amount we spent is well within that. For us, it's about maintaining the quality of the event rather than bean counting.

"What was amazing is that whenever we asked for support people helped us where they could because they have such great affection for the event. It's easy to forget the challenges we've faced in previous years but it's safe to say early in the week we felt pretty challenged. Now I feel proud that we've been able to deliver such great elite fields once again."