Happy 165th birthday Big Ben!

Big Ben is one of London's most famous landmarks.

Although most people refer to the clock tower attached to the Palace of Westminster as Big Ben, it is actually the nickname for the giant bell inside.

Thursday 11 July marks the 165th anniversary of it first striking the hour.

The Tower was completed in 1859. The Great Clock started on 31 May and Big Ben's chimes were heard for the first time on 11 July.

To mark this anniversary, let's find out more about this special bell and clock tower.

When and why was Big Ben built?

This engraving from the Illustrated London News shows the bell being tested with a hammer in 1859

In 1834 a huge fire broke out in the Palace of Westminster - that's also known as the Houses of Parliament where the House of Lords and House of Commons are.

The fire destroyed a lot of the building and when it came to rebuilding parliament decided to add a clock tower as part of the works.

The design for the clock was decided in a competition, in 1846, won by barrister Edmund Beckett Denison.

Construction of the tower began in 1843 but wasn't finished until 1859 - it took 16 years before the tower and clock were completely finished.

Why is it called Big Ben?

The official name of the bell is the Great Bell of Westminster.

Its nickname Big Ben is used more often, but where did it come from?

Big Ben is thought to be named after Sir Benjamin Hall, Chief Commissioner of Works at the time the bell was installed.

That means he oversaw the building as well as other works in the city like the building of a sewage system.

Sir Benjamin was said to be very tall which could explain the Big in the name.

Another rumour is it was named after a boxer Ben Caunt, who was known by the nickname of Big Ben. He was also very big and, just like the bell, is said to have had a booming voice!

How tall is Big Ben's tower?

Imagine 21 London buses sitting on top of each other. That’s the height of the Elizabeth Tower.

It's 96 metres tall. It takes 292 steps to the clock faces and 334 steps to the Belfry where Big Ben, the Great Bell, hangs.

That's pretty tall, but is it the tallest clocktower in the world?

In actual fact the tallest clock tower is the Makkah Clock Royal Tower in Mecca, Saudi Arabia which 601 m (1,972 ft).

Big Ben is the third tallest clock tower in the UK.

How is Big Ben repaired?

It takes a lot of work to maintain the tower, clock and bell and in 2017 the biggest conservation work in its history began.

The work took five years, during which the clock tower was covered in scaffolding and the famous bongs of the bell went silent.

During this time the clock face was cleaned and the dials were revealed to be blue!

One piece of damage was left alone though. In 1858 the 13.7-tonne bell was struck with a hammer, which was two heavy, and a big crack appeared. A lighter hammer was brought in, but the bell itself was never replaced.