Simplify the following text for a Grade 17 native English-speaking person.
Original: The opening ceremony was attended by over 600 guests ; those present included High Commissioners , Deputy High Commissioners , Members of European Parliament , Members of Parliament , Mayors of London boroughs , councilors , university lecturers , and representatives of 17 countries .
Simplified: The opening ceremony was attended by over 600 guests such as High Commissioners , Deputy High Commissioners , Members of European Parliament , Members of Parliament , Mayors of London boroughs , councilors , university lecturers , and representatives of 17 countries .