Simplify the following text for a Grade 6 native English-speaking person.
Original: Lambert died on 21 August 1951 , two days short of his forty-sixth birthday , of pneumonia and undiagnosed diabetes complicated by acute alcoholism , and was buried in Brompton Cemetery , London .
Simplified: Lambert died on 21 August 1951 . He had pneumonia and it was also found that he had diabetes made worse by alcoholism .