Original: Lambert was a prodigy, writing orchestral works from the age of 13, and at 20 received a commission to write a ballet for Sergei Diaghilev's Ballets Russes (Romeo and Juliet).
Simplified: Lambert was a prodigy: he was composing music for orchestra when he was only 13, and when he was 20 he was asked to write a ballet for Serge Diaghilev's world-famous Ballets Russes (Romeo and Juliet).