The original clock mechanism which powered the Welsh version of Big Ben has returned to Cardiff in time to help mark the centenary of the city.
The Pierhead Clock is described as the 'Baby Big Ben'
It has been shipped from the United States where it has been kept by a clock enthusiast for 25 years.
The Pierhead clock mechanism is almost identical to the one which powers the Big Ben clock in London.
Although it will not be fitted back into Cardiff Bay's Pierhead clock, it will form part of a centenary artwork.
The mechanism, which is more than 100 years old, was built for the clock which was installed into the Pierhead Building in 1897 to drive the dials.
It weighs approximately 1,000lb and had to be wound manually once a week for the clock to keep time.
Like clockwork - the mechanism arrives in time for the show
But in 1973, it was taken out of the clock and replaced with an electric drive motor.
A clock enthusiast, recorded only as 'Mr Pearce of London', then bought it at an auction in London and was given permission to remove the supporting steelwork from the Pierhead Building in 1975 and sold it to an American lawyer and clock collector.
Alan Heldman, who bought the mechanism, had it shipped to his home in Birmingham, Alabama.
He had intended to restore a clock using the mechanism but two decades later still had not completed the task.
When Mr Heldman heard about the Pierhead Building and its missing clock mechanism he offered to sell it back to Cardiff, subject to it being restored and put on display for the people of Wales.
The mechanism was built to Lord Grimthorpe's design, by William Potts of Leeds
Mr Heldman told BBC Wales: "I've owned this enormous clock mechanism for about 25 years and have enjoyed showing it to people, but I'm very glad it's back where it deserves to be".
The city council, which already owns the clocks at Cardiff Castle and City Hall, bought the mechanism and it is due to return to the city on Wednesday.
It will form part of a public display at the Port of Cardiff, Past, Present and Future Exhibition before being restored and incorporated into a major public artwork at the Glass Needle Building, opposite the Millennium Plaza at Wood Street Bridge.
Cardiff Lord Mayor Councillor Freda Salway said: "The Pierhead Clock is a landmark that Welsh people hold dear and it is only right that its original mechanism should be brought back to Cardiff to be restored to working as part of Cardiff celebrating 100 years as a city and 50 years as the capital of Wales."
The Port of Cardiff's Past, Present and Future Exhibition runs from 2 August until 24 September at the Old Library, The Hayes, Cardiff.