Simplify the following text for a Grade 7 native English-speaking person.
Original: The Greater London Authority ( GLA ) is the top-tier administrative body for Greater London , England .
Simplified: The Greater London Authority ( GLA ) controls the 1579 kmÂ ( 610 sq . miles ) of Greater London , England , covering the 32 London boroughs and the City of London . The GLA consists of an elected Mayor and the 25 members of the London Assembly .