Geoffrey Mutai has run the fastest marathon in any conditions, with his 2:03:02 in Boston in 2011. His pb is the 2:04:15 he ran when he won in BMW Berlin in 2012. His wins in 2011 and 2013 in New York show that Mutai is quite the talent. His recent win in NYC Half Marathon in March showed his fitness.
In this video, Geoffrey Mutai makes it quite clear he wants the course record at the 2014 Virgin Money London Marathon course.