On the 10th April, London's Big Ben, probably the world's most famous bell and often described as the "sound of Britain", celebrated its 150th birthday.

The bell was first cast at the Bell Foundry Yard - Britain's oldest surviving manufacturing firm - in Whitechapel, east London, on 10th April 1858.

The bell first rang out across London on 31st May 1859 but, just two months later, the bell was cracked as as hammer twice the weight recommended by the foundry was used to strike it. The clock was out of action for three years, but the crack was never repaired. Instead, a lighter hammer was fitted and the bell turned round so as it can strike an undamaged part of the bell. The crack remains today, and it is said that it is the crack that gives the bell its unique sound.

There are many theories as to where Big Ben got its name. A popular one is that, during a meeting of the House of Commons, MPs debated as to what to call the bell. One of the MPs - Sir Benjamin Hall (the comissioner of works for Big Ben) put forward his ideas and then sat down. The MP was quite a large man and was known as "Big Ben", and when another MP then stood up and said "Let's just call it Big Ben!" then the bell was given its famous name.

Contrary to belief, Big Ben is just the bell inside the famous clock tower and not the actual clock tower itself.

Here's a little bit about Big Ben's place of birth. The Bell Foundry Yard in east London is Britain's oldest manufacturing firm, dating back to the mid-1500s...

Ding dong: Historic bell foundry which made Big Ben still going strong 150 years later

11th April 2008
Daily Mail

Big Ben, which celebrated its 150th birthday on Thursday, is situated inside the clock tower of the Palace of Westminster. It is the world's largest four-faced, chiming clock

The bells stand proud waiting to ring out their peals across the world.

One particularly majestic one, destined for a church in the heart of the Cotswolds, even seems to have swallowed this man whole, as he puts the finishing touches to the inside.

The picture was taken inside the venerable Whitechapel Bell Foundry Yard in east London, Britain's oldest manufacturing firm, which dates back to the mid-16th century, and is still going strong today, making (and repairing) clock and tower bells and fulfilling orders from all over the world.

The Bell Foundry Yard in Whitechapel, east London, is Britain's oldest manufacturing firm, dating back to the mid-16th century. This big bell is destined for a church in the Cotswolds.

It is also most famously where Britain's best known bell, Big Ben - the hour bell of Augustus Pugin's Great Clock of Westminster - was cast.

The bell - which is about the celebrate its 150th anniversary - weighs 15 tons, stands at a height of some 7ft and has a diameter of 10ft.

Chiming on the musical note of A, it was finally mounted in the tower alongside four quarter-hour bells, the ring of bells that ring the familiar changes. George Mears, then the master bellfounder and owner of the Whitechapel Bell Foundry, undertook the casting.

Foundry records say that he originally quoted a price of 2,401 for casting the bell (the equivalent of almost 200,000 today) but this was reduced substantially because it was possible to reclaim metal from another earlier bell - leaving the invoice tendered, on May 28, 1858, at 572 (about 60,000 in today's money).

It took a week to break up the earlier bell, three furnaces were required to melt the metal (a hard bronze alloy called 'bell metal') and the huge clay mould was heated all day before the actual casting.

It took 20 minutes to fill the mould with molten metal, and 20 days for the metal to cool.

According to records by the foundry's Alan Hughes: "Transporting Big Ben the few miles from the foundry to the Houses of Parliament was a major event. Traffic stopped as the bell, mounted on a trolley drawn by 16 brightly beribboned horse, made its way over London Bridge, along Borough Road and over Westminster Bridge."

The bells of the Great Clock of Westminster rang across London for the first time on May 31, 1859.

The bell was never officially named, but the legend of it records that the commissioner of works, Sir Benjamin Hall, was responsible for ordering the bell, so it may have been named after him.

Another theory is that the bell was named after a heavyweight boxer of the time, Benjamin Caunt.

Just two months after it officially went into service, Big Ben cracked as a hammer twice the weight recommended by the foundry was used to strike it.

It was taken out of service and for the next three years, the hours were struck on the largest of the quarter-bells.

Eventually, a lighter hammer was fitted, a square piece of metal chipped out of the bell, and the bell given an eighth of a turn to present an undamaged section to the hammer.

This is the bell as we hear it today, the crack giving it its slightly "off" tone.