Simplify the following text for a Grade 6 native English-speaking person.
Original: When he returned to Europe , Walter was invited to play in many places , including Berlin Leipzig , Milan ( La Scala ) and London , where he was chief conductor of the German seasons at Covent Garden from 1924 to 1931 .
Simplified: In London , Walter was chief conductor of the German seasons at Covent Garden from 1924 to 1931 .