The first 21 miles of the annual marathon were dominated by Kenyan runners, followed by the 37,542 accepted applicants who were expected to start the annual run from Blackheath.
Kenya's Wilson Kipsang and Mary Keitany won the men's and women's events respectively in the race.
Kipsang, the second fastest man of all time, won in a time of two hours, four minutes and 44 seconds whilst Mary Keitany won it in a time of 2:18:36, a new Kenyan national record and a personal best.
More than 37,500 runners had registered to start the 2012 Virgin London Marathon, the highest number for two years.
The mass race, started at 9.45am, 45 minutes after Olympic medallist Dorothy Tyler set the elite women on their way from Blackheath, and 25 minutes after the men's and women's wheelchair races began.
Returning champions Emmanuel Mutai and Mary Keitany started as favourites for the elite races in which many of the world greatest marathon runners are competing for total prize money of $313,000 and precious places in their nations' Olympic teams.