Big Ben celebrates 150 years this year. Big Ben is actually the nickname of the bell (the Great Bell) and not the clock (the Great Clock) itself nor the tower. The Clock Tower is sometimes referred to as St Stephen's Tower.
Most people think of Big Ben as the entire package.
The Great Clock told time from 31 May 1859 and the Big Ben, the Great Bell, first chimed on 11 July 1859.
cleaning of the clock faces of the Great Clock is always interesting
Big Ben - the Great Bell