She also set a new course record as she beat Radcliffe's previous women's only record of two hours 17 minutes and 42 seconds, set at the London Marathon in 2005.
It was a fine day for Kenya with Daniel Wanjiru holding off a late charge from Ethiopian Kenenisa Bekele to win the men's race in 2:05.48.
Keitany had been on pace to set the fastest time ever but ended up finishing in 2:17.01 - a record for a women's-only race.
"Her move is just like that of David Rudisha (the two-time Olympic 800m champion) when he broke the world record in London Olympics". Even so, she finished strongly to take second in an Ethiopian record of 2:17:56, which puts her third on the world all-time list.
Bekele finished nine seconds adrift while Wanjiru's compatriot Bedan Karoki was third in 2:07:41.
The 34-year-old was the pre-race favourite and had been on course to break the world record after 13 miles, but he then slowed down and fell behind his rivals.
The 24-year-old Wanjiru had an anxious last two kilometres when Bekele, who had sunk behind just before the 25km mark, ploughed his way back.
If you are an experienced runner, you may be able to automatically qualify by "good-for-age" entry.
Marie, said: "I am running for Severn Hospice as they recently looked after a very close friend of mine in his final days, so it is a charity very close to my heart". Ally Dixon was the fastest British woman home in a personal best to book her place for London, where she will be joined by Charlotte Purdue and, most likely, the third-placed Briton, Tracy Barlow.
It was a do-or-die fight in the race the former colonial master had billed "unofficial Kenyan world championship trials".
Thousands of runners will be pounding the streets of the capital tomorrow for the 37th London Marathon - here we shine the spotlight on a few from the Hitchin area.
The women's-only record was designated after track and field's governing body, the International Association of Athletics Federation, changed the criteria for marathon world records in 2011 so that the women's record had to be set in a women-only race.
"I've been preparing to win this race since Christmas so I'm very grateful that I achieved my goal". From there it was becoming tougher and tougher.
Father-of-two Michael Lilley, from Blackburn, will be running his fourth marathon this year as he aims to complete 12 races in 12 months for Macmillan Cancer Support. "The sun was coming and the day was attractive - but we don't need too much sun!"
There was a British victor in the wheelchair race, with David Weir storming to his seventh victory in the event to end four years of frustration since his last success. I felt my hamstring and my right calf.
"All I was thinking was "win, win, win".
She said: "Sarcoma is often misdiagnosed, as it was in my mum's case".