Tergat

The Kenyan set a new world record of two hours, four minutes and 55 seconds at the Berlin Marathon in September.

He will face Olympic champion - and this year's winner - Gezahegne Abera of Ethiopia and Morocco's world champion Jaouad Gahrib in London.

"London is special for me because in a sense London made me," said Tergat.

"I cut my teeth on the marathon here and now I am coming back as world record holder.

"But with the field that has been assembled I shall have to watch my step."

Tergat's best performance in London was a second place as Khalid Khannouchi broke the world record in 2002.

What remains impossible is running a marathon in under two hours Paul Tergat

Next year's field will include 10 men who have run a marathon inside 2:07.

Sammy Korir, who finished one second behind Tergat in Berlin to become the second fastest of all time, Chicago Marathon runner-up Daniel Njenga and fellow Kenyan Evans Rutto will also be in action.

The Athens marathon will be Tergat's last for his country, but he will continue to race on as an individual.

"I will run as long as I am still able to concentrate and to focus," said Tergat, who has won two Olympic silver medals in the 10,000m.

"It will be a few more years before I retire. I feel that I still have a lot of mental power to concentrate for very important meetings."

Tergat's world record time knocked 43 seconds off the previous best and was the biggest improvement in the world record in five years.

But he thinks two hours is beyond mankind.

"Next day [after the Berlin Marathon] I was not able to walk. When I finished I was not even able to bend down to undo my shoes," he said.

"I believe that records are set to be broken in the future. To get under 2:04 would take a great effort and to fall lower is possible.

"What remains impossible is running a marathon in under two hours."