BERLIN (Reuters) - Kenyan Patrick Makau shattered the world mens marathon record by 21 seconds on Sunday when he clocked two hours three minutes 38 seconds over the fast, flat Berlin course on a warm, sunny morning. Makau ran alone for the final 12 kms to break the previous mark of 2:03:59 set by Ethiopian Haile Gebrselassie on the same course three years ago. It was the fifth time the mens world record has fallen on the 42.195-km race through the heart of the German capital. The 26-old-Kenyan won the Berlin race last year and finished third in London this year after falling 22 kms into the race. A former half-marathoner, who has broken the 60-minute barrier mark a record eight times, his previous best marathon mark was 2:04:48 in Rotterdam last year. What I can say is that we have started a new generation in marathon running, Makau told reporters. This is the greatest day of my running life. When I woke up today my body didnt feel very good but at 25 kms I felt I could break the world record. Makaus team mate Florence Kiplagat, the world half-marathon champion, won the womens race in 2:19:44 in her first completed marathon. Kiplagat and world record holder Paula Radcliffe, running her first marathon since finishing fourth in New York two years ago, took the early lead followed by Germanys twice Berlin champion Irina Mikitenko. At 17 kms, Kiplagat began to stride away from the Briton and at the halfway stage held a 19-second lead. Mikitenko overhauled Radcliffe to finish second in 2:22:18 with Radcliffe third in 2:23:46, comfortably inside the British qualifying time for next years London Olympics. Kiplagat, who failed to finish her only previous marathon in Boston this year, said she had not been bothered by the 22 degrees Celsius heat. I would be delighted if I could run in the Olympic marathon, she said. Radcliffe, whose training has been hampered by back and thyroid problems, said 2011 had been a tough year. At least I have the Olympic qualifying time, I now have to build on that for London, she said. Gebrselassie, who has won the Berlin marathon four times, headed the leading group until just before the 27-km mark when he pulled up in obvious pain. He bent over double but then stepped back on to the road within a minute but was unable to finish the race. Pacemaker Stephen Kwelio decided not to drop out of the mens race and was rewarded with second place ahead of Kenyan compatriots Edwin Kimaiyo and Felix Limo.