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Four key working parts of London's iconic 129-year-old Tower Bridge have been removed and replaced for the first time in decades.

The two-metre long bolts lock the moving parts of the bridge, known as bascules, in place when it is lowered for traffic and pedestrians to cross.

Overnight closures remain in place at the historic landmark while the planned maintenance takes place.

About 40,000 people and 21,000 vehicles usually cross the bridge every day.

It is lifted roughly 900 times a year to let boats pass underneath.

City Bridge Foundation, the 900-year-old charity which owns and maintains Tower Bridge as well as four other Thames crossings, is carrying out the works.

Paul Monaghan, assistant director of engineering for City Bridge Foundation, said: "As well as being London's defining landmark, Tower Bridge is a key part of the capital's transport infrastructure.

"As a bridge with moving parts, it's inevitable that we will see wear and tear, but carrying out planned work like this avoids the need for more disruptive and costly repairs further down the line."

He added: "Doing these kind of jobs at night means we keep London moving and minimise disruption to motorists, pedestrians and the many tourists who come to enjoy the visitor attraction."

It follows previous repair work in August, when the crossing was left in a raised position for long periods while metal plates in the moving parts of the bridge were replaced due to damage through wear and tear.

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