As a junior athlete in 1999, Lambert finished 3rd at the European Junior Championships and ran the fastest time in the world over 200m for an U20 athlete. Named captain of the Great British Junior team in 2000, he was unable to compete for the majority of the season due to a hamstring injury but left the age group ranked 3rd on the national all-time list. At Harvard, Lambert broke 5 college and 3 Ivy League records (for the 60m, 100m and 200m), winning 6 Ivy League titles and finishing 4th in the 2003 NCAA Men's Outdoor Track and Field Championship, becoming an NCAA All-American.