The 32-year-old defending champion, who appeared yesterday alongside Britain's latest high profile woman marathon runner Marian Sutton, has grown more cautious in her pre-race predictions over the years.
The runner who said before her first London race in 1993 that she would not be surprised to run under 2hr 20min - more than a minute inside the world best - has learned from experience how capricious the 26.2- mile distance can be. Hers is now a tempered optimism.
"There are 10 athletes out there who can win this thing," she said. "I know that I will have to be at my very best to win. Fortunately I have had the ideal preparation. There has been no break in my training since Christmas and it is well within my capabilities."
McColgan, whose hopes of earning a medal at last year's Olympics were undermined by blood poisoning following an insect bite, plans to make up for the experience at Sydney in three years' time.
In the meantime, she is thinking positively about running in this summer's World Championships in Athens - for which Sunday's race doubles as the British trial - despite the widespread fears about the heat and pollution there. "If I decide to run and I am selected then I will definitely go to Athens."
Sutton, who put herself on the map with her victory in Chicago last October in a time of 2:30:41, is less certain about Athens. The 6ft runner was, in her own words, "devastated" by the decision of Britain's selectors not to choose her for the Olympic team last summer, and had travelled to Chicago determined to prove a point.
But looking forward to this year's World Championships, to be held in the summer smog of Athens, is something which generates ambivalence, at best. "I'll see what happens here before making any decisions about the World Championships," she said yesterday. "I don't particularly relish the idea of running 26 miles in Athens."
The 33-year-old solicitor's clerk, who trains on her own in her Cornish home town of Looe, improved her personal best by nearly two minutes to earn what was her first marathon win. "A sub-2:30 run is within me," she said. "But maybe not on Sunday. I have to be sensible about the pace. I have times in mind but it's important to stick to what I know."
For all that her Chicago win surprised many people - not least, one suspects, the British selectors - she herself had gone into the race confident of a very good performance, if not outright victory. "I never had any doubt about my own ability," she said. "I always thought that I would reach this level so it's been no surprise to me. And there is certainly more to come."
In truth, there will have to be if she is to maintain contact with an impressively strong field including McColgan, the Portuguese world and European champion Manuela Machado, and Ren Xiujuan of China, who took the world half-marathon title last October and has won three of her five marathon outings to date despite being only 22.
Ren has asked for a pacemaker to take her through the half-way mark on world record schedule with the aim of breaking the world best for the distance held by Norway's Ingrid Kristiansen, who ran 2:21:06 in London 12 years ago.
David Bedford, the race director of the London Marathon, believes that tomorrow's race could be the best in the event's 16-year history. "We have assembled what I think are two of the most talented fields ever put together for a marathon," the former 10,000 metres world record holder said.
The obvious attraction in the men's race is the Olympic champion, Josiah Thugwane, and Bedford is known to have spent a considerable amount of his pounds 625,000 budget in obtaining the South African's services. Thugwane is reputed to have been paid $100,000 (pounds 62,500) to run although Bedford refused to name the figure. "We never discuss appearance fees but getting an Olympic champion in the race was a priority," he said.
The 5ft 2in South African showed huge strength in taking the Olympic title, but his relatively slow personal best of 2:11:46 - run, admittedly, in the Atlanta heat - and his relative lack of experience in big city marathons has left many observers looking towards the more tried and tested talents of Portugal's Antonio Pinto, winner in London in 1992 and third in 1995, and Australia's Steve Moneghetti, the runner-up in 1989 and 1995. The reigning world half-marathon champion, Stefano Baldini of Italy, and America's Jerry Lawson are also men to look out for.
But the most intriguing aspect of the men's race appears to be the first meeting of Britain's top two men - Paul Evans, like Sutton a winner in Chicago, and Richard Nerurkar, who was fifth in Atlanta.
"What Richard did in the Olympic marathon was outstanding," Evans said. "To come fifth in those conditions was an unbelievable performance. He's going to be a tough nut to crack."
The question is, if Evans does crack it, will that be enough to become the first British male winner here since Eamonn Martin in 1993?