Britain's Dave Weir is confident he can retain his wheelchair title in Sunday's Flora London Marathon.
Weir's victory last year signalled the start of a memorable year
Weir stormed to success in last year's race in a course record time of one hour, 29 minutes and 48 seconds and believes he can better than on Sunday.
"The conditions look like being good so it should be a very fast race," Weir told BBC Sport.
"Winning in London this year would probably be the best ever victory of my career but it will be tough."
Weir, who also won in 2002, has recovered from a heavy cold to take part in the race, organised by Disability Sport Events, and warmed up for his challenge with second place behind Australian Kurt Fearnley in last month's Los Angeles Marathon.
Fearnley is the current king of the distance and he will be chasing his seventh consecutive marathon win when he makes his London debut.
Also in the field are South African Ernst van Dyk, who crashed in last year's race and Mexico's Saul Mendoza, the winner in 2004 and 2005.
But Weir knows that Fearnley is a real threat to his crown.
"Kurt is a strong all-rounder, even if he doesn't know the course as well as I do, and it is difficult to break him," he said.
Ade Adepitan will be making his marathon debut in London
"He is good on the uphill and downhill sections and also on the straight but he's done so many marathons that maybe he will be tired by London.
"I will be sticking with him wherever he goes in the race because he will be challenging for the lead, and I know he will do the same with me. It could be a real battle to the end, although you don't know who else will be in the pack.
"The pressure of being defending champions isn't something that bothers me and being the one that the others want to beat makes me train harder.
"Because we don't have a major championship this year, this is one of my most important races of the year."
Among the other British competitors are Brian Alldis, who was fifth last year, and former Paralympic wheelchair basketball player and BBC Television personality Ade Adepitan.
Adepitan is making his marathon debut and will be raising funds for WheelPower and the Brain and Spine Foundation. He has been given some training tips from Weir, who is impressed with how well he has done.
"I think Ade has taken to the training very well - much quicker than I thought he would and he looks like he could be a very good sprinter if he wanted to keep it on," he said.
"I've given him some advice and I think he will do well and certainly get around the course."
Blackpool racer Shelly Woods leads the British challenge in the women's race, with the 20-year-old hoping to make it third-time lucky after second place behind Italy's Francesca Porcellato in the last two years.
"My training has gone well and my performances and times this year show I'm going in the right direction," she said.
"Francesca has won four times in a row in London and is the world marathon record holder so it will be tough but I'm confident.
"I would love to win because it is a big race for any British athlete and it is the most high-profile race I get to compete in at home."