The ornate decoration on the Elizabeth Tower's upper floors owes much to Augustus Welby Pugin's influence on the main architect, Sir Charles Barry. The two architects collaborated successfully on the Palace of Westminster's neo-Gothic style which is displayed to great effect on the clock dials.
Each dial is 7m in diameter and is made from cast iron. Each dial contains 324 separate pieces of pot opal glass, a type of glass with an opaque finish.
The hour figure of four o'clock is shown by the Roman numeral IV, rather than IIII, as is more commonly used on clock dials.
Under each clock dial there is a Latin inscription carved in stone: "Domine Salvam fac Reginam nostrum Victoriam primam" which means "O Lord, save our Queen Victoria the First."
During a week in August 2014, a team of specialist technicians abseiled down to clean and survey the clock dials. As each clock dial was inspected both the minute and hour hands were positioned at 12 o'clock to facilitate access.
Find out more about Big Ben and the Elizabeth Tower