Liz McColgan is threatening to exploit Catherina McKiernan's relative lack of experience in road running when the Cavan athlete seeks to join the list of winners of the London Marathon tomorrow morning.

It's the biggest test so far of McKiernan's remarkably successful conversion to road running after significant careers in track and cross country competition.

Since her success in the Dublin mini marathon, she has put together a sequence of 13 wins - a couple of them in cross country races - but if McColgan's judgment is right, it's all going to end some time around noon tomorrow.

"There can be nothing but admiration for the way Catherina ran her first marathon in Berlin in September - to finish in two hours 23 minutes 44 seconds was incredible," she said.

"I've run against her only once this season and again, she looked sharp, in the Lisbon half marathon. But that was only a stage in both our preparations for the full marathon in London - it has no real relevance to Sunday's race.

"Experience is important in any sport and I know exactly what it takes to win this race. I'm happy with the way my preparations have gone - I believe I'm ready for a big run."

McColgan has won the race once and been caught on two other occasions when she seemed certain to win. Even now her fate in last year's race, when she was passed almost on the finish line by the Kenyan, Joyce Chepchumba, is a subject of some astonishment.

It is a measure, however, of the impact McKiernan has made in the last year that in spite of her immaturity in this facet of athletics, she is still the bookies' favourite to win the race at odds of even money. McColgan is being quoted at 11 to 4 with Chepchumba at 4 to 1.

As a track runner, McKiernan is one of the most experienced around. Although she has never won a major title, she can reflect on two Olympic challenges at Barcelona and Atlanta, two World Championships and a similar number of European Championship expeditions.

In cross country, her record is more formidable still. A former European champion, she finished second in the World Championships on four occasions and won the IAAF's world cross country title twice.

Yet, almost certainly, tomorrow's race is the most important of her career, representing the gateway to substantial earnings. In addition to an attractive race fee, there is the prospect of a £65,000 sterling bonus if she breaks the new world record of two hours 20 minutes and 47 seconds set by the Kenyan, Tegla Loroupe in Rotterdam last Sunday.

That achievement, incidentally, was the subject of some caustic comment by McColgan during her press conference yesterday. She questioned the propriety of Loroupe being helped by her male compatriots, who ran with her in the race. McColgan suggested that if this was going to be allowed then maybe there should be different records for women-only and mixed events.

A contingent of around 100 supporters from Co Cavan is due in London today, to provide vocal support for McKiernan. Unless the pace in the middle stages of the race is exceptionally fast, however, their chances of seeing their favourite set a new record are slim.

"My first priority is to win the race," says McKiernan. "The idea of setting a record hasn't even entered my head. All that really concerns me when I go to the starting line is that I get to the other end feeling well.

"I've tried to detach myself from all the hype and so far I think I'm succeeding. It may be a big race, but irrespective of who wins the sun is still going to come up the following morning."

The withdrawal of the world champion, Hiromi Suzuki of Japan, deprives the race of one of the biggest of the celebrity athletes. Yet there is still enough quality left in the entry to ensure that the Irish woman is going to have to produce one of the great runs of her career to win it.

Chepchumba hasn't been particularly impressive in cross country competition in recent months, but like McColgan she has pitched her season to arrive in London in peak condition. And that is equally true of Belgium's Narleen Renders and England's Marian Sutton, who both finished behind McKiernan in a 10 kilometres race in Alabama last month.

Sutton, a previous winner of the Rotterdam marathon, believes that McKiernan is far from invincible and aims to be among those who will prove it. "Catherina has been in awesome form of late but all the pressure will now be on her. And she may just discover that her second marathon is harder than the first."

That's a sentiment which has been articulated in the past, but the hope is that when the women's race reaches into its final phase McKiernan will be in front and, profiting from McColgan's experience last year, will manage to stay there.

Noel Berkeley is among the Irish entries for the men's event, in which Antonio Pinto of Portugal, a former winner, is favourite to beat the Olympic champion, Josia Thugwane of South Africa, world champion Abel Anton and the formidable Kenyan Elijah Lagat.