The clock was the largest in the world and is still the largest in Great-Britain. The clock faces have a diameter of almost 25ft (7.5m). The hour hand is 9ft or 2.7m long and the minute hand measures 14ft (4.25m) long.
The clock is known for its reliability, it has rarely failed during its long life span. Even after the nearby House of Commons was destroyed by bombing during World War II, the clock kept on chiming. The clock's mechanism, designed by Edmund Beckett Denison, has a remarkable accuracy. The clock's rate is adjusted by simply adding small pennies on the shoulder of the pendulum.