Aussie marathon pair eye history in London

Joe Barton
AAP

Two Australians will look to achieve history at the London Marathon this weekend.

Four-time Olympian Craig Mottram, 35, is seeking to become the first Australian track and field athlete to reach a fifth Games while fellow Melburnian Shawn Forrest will on Sunday become the first man with type-one diabetes to race in the elite section of a major city marathon.

His extraordinary feat could also lead to a place in Australia's track and field team heading to Rio in July - though Mottram, despite previously being a 5000m specialist, is favoured to post the faster time on Sunday.

And with Michael Shelley certain to be picked, having run 2:11:19 and 2:12:20 in the qualifying period, Mottram has his eye on one of the two remaining marathon spots.

The qualifying mark of 2:19.00 has been cracked multiple times, but Scott Westcott and Brad Milosevic - the two quickest behind Shelley - have posted times Mottram believes are attainable this weekend.

Westcott's 2:15.30 and Milosevic's 2:16.00, while inside the qualifying time, provide no guarantees that they'll be in the Rio team.

However a 2:13.00, which is what Mottram is targeting in London, would book his ticket.

In Mottram's previous four Olympics, he competed in the 5000m event - finishing eighth at Athens - and he doesn't shy away from the challenge being presented by the longest distance race on offer.

Forrest, meanwhile, was diagnosed with type-one diabetes in 2014 and didn't race at all the following year.

But he refuses to give up on securing a maiden Olympic berth.

Should the 32-year-old better his personal best time of 2:14.36, set in 2012, Forrest would also firmly put himself in the selection picture.

"I have always wanted to run the London Marathon and why couldn't I make that Olympic team?" Forrest said.

"I believe anything is possible."

Cassie Fien will run in the women's elite race, while wheelchair superstar and course record holder Kurt Fearnley will be chasing another podium finish after claiming third in last week's Boston Marathon.