The glass walkway across one of London's most famous landmarks has been replaced - a feat that took 12 hours to complete.

Tower Bridge, for the first time since its glass floors were installed in the High-level Walkways nearly 10 years ago, has shared the process of replacing the top layer of the glass.

Workers removed the old layer - at 42 meters above the Thames - on the evening of June 17 and completed the installation of the new one on June 18.

The team removed the old layer on June 17The team removed the old layer on June 17 (Image: Tower Bridge)

This task happens every few years to ensure that visitors can get the best views and the best selfies from the top of the bridge.

Carried out by a team of seven glazing specialists from G&G Glass, it took a total of 12 hours to replace the glass in the East Walkway.

Similar works on the West Walkway are set to take place later this year.

The 11.5m-long glass floors offer visitors a unique view of people crossing the bridge below and boats sailing underneath.

The work takes place at 42 metres above the ThamesThe work took place at 42 metres above the Thames (Image: Tower Bridge)

If timed right, visitors may also enjoy a bird's-eye view of the bridge's lifts, which occur around 800 times a year to allow larger vessels to pass.

Rob Woollard, principal attraction manager for Tower Bridge, said: "Since they were installed almost 10 years ago, the Glass Floors in our High-level Walkways have been a huge hit with visitors.

"We’re thrilled to be able to share this intricate process which ensures everyone who visits can continue to experience the best views possible through the iconic Glass Floors and enjoy a memorable day out at London’s defining landmark."

The glass floors can support the weight of six elephantsThe glass floors can support the weight of six elephants (Image: Tower Bridge)

The glass floors are made up of six panels that weigh 530 kilograms each, and are capable of holding the weight of four London black cabs or six elephants.

The original installation of the floors in 2014 took six weeks and a team of 20 workers.

The replacement of the glass floor comes as Tower Bridge prepares to celebrate its 130th anniversary.

The shiny new walkway is ready for visitors as the landmark celebrates its 130th birthdayThe shiny new walkway is ready for visitors as the landmark celebrates its 130th birthday (Image: Tower Bridge)

From June 22, the landmark will host a free, summer-long exhibition: 'Launching a Landmark: The Unseen Opening Weeks'.

This exhibition will display photography from the Bridge’s final few weeks of construction and public opening 130 years ago in 1894.

For more information about Tower Bridge, the glass floors, or the upcoming exhibition, visit the Tower Bridge website.