The Instant Expert: You can depend on Ben

Britain's best-known landmark celebrates a significant anniversary today.

THE BASICS On this day in 1859, 16 white horses pulled Big Ben from Whitechapel Bell Foundry to its present home at the Palace of Westminster, London. Big Ben is the nickname for the clock, the bell and the Clock Tower at the north end of the palace. As the biggest four-faced chiming clock in the world, it is an icon of London and the UK and one of the world's most recognisable buildings. Officially, the Clock Tower's bell is called the Great Bell, although Big Ben originally referred to the Great Bell alone.

HOW IT STARTED Fire gutted the Palace of Westminster in 1834. Ten years later it was decided the new buildings for the Houses of Parliament should include a tower and a clock.

AN ARCHITECTURAL WONDER? The new Parliament buildings were constructed in neo-Gothic style by the architect Sir Charles Barry. Barry engaged the architect and designer Augustus Pugin to design the Clock Tower but must have been a demanding boss, as it was poor Pugin's last work before he descended into madness and death.

WHAT ABOUT THOSE BONGS? The famous "bongs" were first heard on July 11, 1859, after the Great Clock had started on May 31. The chimes were first broadcast, by the BBC, on New Year's Eve 1923, a tradition that continues. ITN's long-running news bulletin News At Ten punctuates the main headline at the start of the programme with a resounding bong.

A MONUMENT TO GOOD TIMEKEEPING THEN? Yes, but not always. After Big Ben first rang out, its bell (the second one) cracked two months later and the quarter bells - which chime on each passing quarter-hour - struck the hour for busy Londoners. A lighter bell, the one heard today, was fitted shortly afterwards. Despite the German air force's best efforts, the clock (with blacked-out faces) ran accurately and chimed throughout the Blitz. Unfortunately, it broke down in 1976 for 26 days and needed major reconstruction due to technical difficulties.

AND TRADITION? Absolutely. In 1980, when the BBC announced that Big Ben was going digital, the broadcaster's phone lines were jammed with angry protests. However, the outrage was ill-founded, as the broadcast turned out to be an April Fool's Day hoax.

HOW BIG IS BIG BEN? Well, the Clock Tower is 96 metres high and 12m square, and the bell inside the tower weighs 13,760 kilograms. The four clock faces, which are lit at night, measure 49.15 square metres and are 55m above ground. Big Ben's minute hands are 4.26m long. The figures on the face of Big Ben are 0.6m high. At the base of each clock dial in gilt letters is the Latin inscription: "Domine salvam fac reginam nostram victoriam primam" (O Lord keep safe our Queen Victoria the First).

WHAT'S WITH THE NAME? Big Ben is believed to have been borrowed from a heavyweight boxing champion of the time, Benjamin Caunt. During Victorian times, it was common to refer to anything that was the heaviest in its class by the nickname.

THE LEANING TOWER OF LONDON? It is. As ground conditions have changed over the years, the tower leans to the north-west, by 22cm.

SO, CAN I VISIT IT? Despite being one of the world's most famous tourist attractions, the tower is not open to foreign visitors, though United Kingdom residents are able to arrange tours through their Member of Parliament. However, visitors must climb the 334 steps to the belfry as there is not a lift.

Big Ben on the big screen

The landmark has been a popular choice for filmmakers who want to ensure their viewers know a scene is taking place in the UK. Five of the most notable appearances are:

PETER PAN (1953) In the famous Walt Disney cartoon, the boy who never grew up lands on the clock with Wendy and her brothers before heading off to Neverland.

THUNDERBALL (1965) In the fourth James Bond film, a mistaken extra strike of Big Ben on the hour is executed by the criminal organisation Spectre to signify that the British government has agreed to its nuclear extortion demands.

QUEEN KONG (1976) A comedy remake of King Kong (1933) in which Big Ben is substituted for the Empire State Building.

THE THIRTY NINE STEPS (1978) Richard Hannay (played by Robert Powell) clings to the minute hand of Big Ben's western dial in a bid to stop the clock's progress and prevent a linked bomb from exploding.

SHANGHAI KNIGHTS (2003) This Jackie Chan feature has sword fighting action inside and outside the Clock Tower.