Glory and Games places up for grabs on London streets

Kenyans chase victory and Olympic spots while British runners have their last chance to qualify

Claire Hallissey (pictured) seems best placed to target Jo Pavey's time (Getty Images)

There is an elephant on the course of tomorrow morning's 32nd London Marathon. It is an Olympic year, and for the elite British runners a home Olympic year – so tomorrow, more than ever, the 26 miles will be sliced into a series of match races defined by nationality as athletes look to clinch places among the cast of the greatest show on earth.

Click HERE to view tomorrow's London Marathon route graphic

The London Marathon is a spectacle in its own right but the leading men and women will be running with half an eye on the Olympics, from the six Kenyan men battling for three places to the cluster of British women looking to take the one remaining spot, to those in a competitive wheelchair field.

"Everyone is going to be on top of their game because it's an Olympic year," said David Weir, who is bidding to equal Tanni Grey-Thompson's record of six wheelchair wins. Does a good London Marathon put down an Olympic marker? "Massively," said Weir.

Paula Radcliffe and Mara Yamauchi have tied up two of the British women's Games places, leaving one to be raced for. Experience favours the 37-year-old Liz Yelling, already a double Olympian, but form does not. Jo Pavey, who like Radcliffe and Yamauchi is not racing tomorrow, posted the time to beat in London last year, 2hr 28min 24sec, and unless that is bettered now she will run in London in August. Claire Hallissey, a 29-year-old with a PhD in immunology, appears best placed to target Pavey's time. Last year she took seven minutes off her personal best, recording 2.29:27 in Chicago, and she is confident of going faster this year after training in Colorado. The marathon debutant Freya Murray, a multiple Scottish cross-country champion, could also spring a surprise.

Tomorrow the Kenyan Mary Keitany is a strong favourite to retain the women's title she won so emphatically last year. Among the men, the finish should feature the Kenyan sextet, including last year's winner Emmanuel Mutai and the two who followed him home in Martin Lel and Patrick Makau, the world record holder – while further back two Britons will be chasing an Olympic dream. Benedict Whitby and Lee Merrien need to run inside 2.12:00, the qualifying time for the British team.

They will have pace-making assistance from Scott Overall, the only British man to have qualified so far. As a City of London policeman, Whitby will at least know his way around.

"There will be some nervousness and tension," said Abel Kirui, Kenya's world champion. "It's unpredictable. Only God knows." Kenya's selectors will make up their mind by the end of the month, Britain's by Monday.

The last word belongs to Weir, who took his first London title in 2002 and won four medals at the Beijing Paralympics. "It's jumped up another level if you look at the field here," said the 32-year-old. "It's going to be tough."