Work on Shrewsbury's 117-year-old, Grade II listed Severn Bridge Junction signal box has been completed – weatherproofing the building, with double glazed windows and timber cladding added.
The historic building has its original 180 levers inside, with 89 still in use today and is responsible for signalling around 280 trains every day.
The £250,000 refurbishment of the Edwardian building has been carried out by Network Rail and MPH Construction.
The project, partly funded by the Railway Heritage Trust, has allowed the entire three-storey building to be weatherproofed.
As part of the refurbishment, the original single-glazed windows, installed when the building first opened in 1903, have been replaced with new double-glazed units.
Other pieces of work include new timber cladding and holding repairs to the external walkway gantry and a full exterior paint job – including the famous ‘Shrewsbury’ signs that greet passengers travelling in and out of the town by train.
Darren McKenna, asset engineer at Network Rail, said they had been mindful to ensure the building did not lose its Edwardian character.
He said: "It's not until you can get up close to this iconic structure that you can appreciate how well built and unique it is. Working on this refurbishment was an absolute pleasure.
“The gantry repair was a big job and involved rope access teams working day and night to strengthen and replace the boards.
“We gave very careful consideration to a sympathetic repair that has managed to maintain the building’s Edwardian character while securing its future for many years to come.
“The mechanical signal box, now the world’s largest operational mechanical signal box in the world, still plays a fundamental part on the railway by controlling safe access in and out of Shrewsbury station.”
Darren Peake, signaller at Network Rail who works in the historic building, added: “I have been working at this signal box for around 13 years and I can tell you these improvements will make a huge difference to us, including being warmer in the winter with the new windows.
"We used to have to put pieces of paper in the gaps of the old ones. In fact, when they replaced the windows, they found newspaper cuttings behind the frames from the 1960s.
"The history of this building is fascinating, and I am extremely proud to work from here."
Gareth Ellis, Construction Manager at MPH Construction Ltd, added: “We started on site in October last year and knew that this was going to be a challenging project; restoring a Grade II listed building, working at height and being completely surrounded by track.
“However, we couldn’t turn down the opportunity to work on this iconic piece of railway infrastructure and even carried out some extra works, such as renewing the eye-catching Shrewsbury sign for passengers to see.
“It has been a unique and fascinating project to work on.”
Andy Savage, executive director, Railway Heritage Trust, said: "We were delighted to give a grant towards the restoration of this iconic signal box, which clearly will have a long-term future.
“We congratulate the Network Rail team for their careful work in restoring the building.”
Engineers worked for more than 300 days, restoring this crucial part of the railway infrastructure which is a vital link for passengers and freight travelling between Wales & Borders and the rest of Britain.
Further improvements are also planned for the interior of the signal box over the next few weeks.