Next Sunday's (October 4) 40th running of the London Marathon could be the most unpredictable ever, according to race director Hugh Brasher.
The challenges of training during the coronavirus pandemic – which caused the race to be switched from its original date of April 26 – have made it difficult to gauge how individual runners will perform on the day.
Only elite athletes will compete on a closed loop circuit within St James's Park.
Reflecting upon the likely result, Brasher told insidethegames: "I think the journey that each elite runner has been on has involved different challenges each will have had to overcome or adapt to.
"I think that is one of the huge unknowns about what will happen on October 4.
"It really is.
"You could have a form book going judged on past races, but I am not sure it will count nearly as much as normally in terms of performance on the day.
"What we have tried to do – we had this amazing field for the 40th race, and we have tried to replicate that as much as possible for the October event, to stick with the athletes that were coming to us and it has been great that they have stayed with us."
The men's race will feature Kenya's Olympic champion and defending champion Eliud Kipchoge, who will be seeking a hat-trick of victories and a fifth win within six years.
He will be joined by multiple Olympic and world track champion Kenenisa Bekele of Ethiopia, while the women's race will feature Kenya's world record holder Brigid Kosgei and world champion Ruth Chepngetich.
Kipchoge, who became the first athlete to run the distance in under two hours last October in a specially staged event in Vienna's Prater Park, holds the official world record of 2 hours 1min 39sec, while Bekele has the second fastest time on record, just two seconds slower.
But both men have had to adapt their training regimes because of complications brought about by the COVID-19 pandemic, and Brasher alluded to further difficulties that have been encountered by Bekele.
"We know that Ethiopia has had some difficult times politically over the past few months and that Kenenisa has not always been able to train in the way he would normally," he said.
A world record total of 45,000 entrants are preparing to take part in the virtual London Marathon.
Each runner will have a minute less than 24 hours to run the distance, starting from midnight on Saturday (October 3) and will track their run and time via an official app.
For today's Big Read on the London Marathon click here.