Simplify the following text for a Grade 9 native English-speaking person.
Original: In London , the Metropolitan Police and the City of London Police are led by Commissioners rather than Chief Constables . Chief Constable was , however , a lower rank in the Metropolitan Police which existed between 1886 and 1946 .
Simplified: Every police force in the United Kingdom has a Chief Constable except the City of London Police and the Metropolitan Police Service .