The centre of Brighton will be closed early on Monday morning as work to restore the Clock Tower nears completion.
A new bronze mast, complete with a gilded copper ball weighing 100kg, will be lifted and secured to the top of the tower.
The historic tower, built for Queen Victoria's Golden Jubilee, has been out of action since May last year.
Now the golden ball will be restored so it glides up and down the mast every hour as it did in Victorian times.
To ensure safety, the work will be carried out between 3am and 6am on Monday with all nearby roads and pavements closed.
Environment councillor Chris Morley said: "This will be a historic moment. The Clock Tower has not been fully operational for 100 years.
"It is entirely fitting that we are bringing it back to full working order during Queen Elizabeth's Golden Jubilee year."
The rising and falling ball was originally stopped in 1902 as the noise was said to be frightening the horses and annoying neighbours.
After the mast and ball have been installed, scaffolding will remain in place while the finishing touches are added.
These include painting and additional gilding work to the scales at the top of the tower in accordance with the original appearance, further cleaning and reinstating the refurbished clock hands.
The work should be completed by the end of September but dry weather is essential to carry out the gilding.
Total cost of the completed project will be about £100,000, including contributions from Boots and The Regency Society.
The time ball was installed by Magnus Volk, who also created the seafront electric railway.
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