Refurb of world’s largest working mechanical signal box completes

The largest working mechanical signal box in the world has just had its biggest refurbishment in more than a decade.

We’ve worked with contractor MPH Construction since October to sensitively carry out £250,000 of improvements to Severn Bridge Junction and keep it running for the future.

The 117-year-old, grade II listed building stands just outside Shrewsbury railway station – a vital link for passengers and freight travelling between the Wales and the Borders area and the rest of Britain.

It still has its original 180 levers inside, all dating from 1903. Our modern day signallers use 89 of those levers to signal about 280 trains every day.

Severn Bridge Junction is one of our most famous and striking signal boxes. You may have seen it in the first series of The Architecture the Railways built on Yesterday.

It stands three storeys high in the middle of the tracks outside the station – once a hub of significant commercial activity.

The Architecture the Railways Built – Severn Bridge Junction

The Architecture the Railways Built – Ffestiniog Railway

Meet Britain’s most remote signal box

Severn Bridge Junction signal box with scaffolding, daytime
Workers restore Severn Bridge Junction

Watch this video to see the restoration up close:

Fit for the future

The refurbishment project, partly funded by the Railway Heritage Trust, has weather proofed the entire building.

We’ve replaced the original single-glazed windows – installed when the building first opened in 1904 – with new double-glazed units.

Close up of Shrewsbury sign on the exterior of Severn Bridge Junction signal box, daytime
The original station sign, restored

Other improvements include new timber cladding and holding repairs to the external walkway gantry. A full exterior paint job included the famous Shrewsbury signs that greet passengers travelling in and out the historic town by train.

Darren McKenna, an asset engineer at Network Rail, 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.”

Andy Savage, executive director of the Railway Heritage Trust, said he was “delighted” with the restoration, and praised the care given to repairing the box, and particularly the walkways around it.  

He said: “Network Rail has put metal plates behind the internal skirting board so the load from the walkway on the bolts is now spread by the plates. It’s a really clever and well-done piece of work that doesn’t destroy the original heritage but gives the structural safety for staff on the walkways that is absolutely needed.” 

The project at a glance

Engineers worked for more than 300 days to restore the exterior.

The box is grade II listed so a conservation officer pre-approved all plans to ensure the building maintained its listed status.

The Railway Heritage Trust – funded by Network Rail – contributed £50,000 to the new windows. The trust had previously contributed about £100,000 to the station’s canopies in 2018 to 2019.

The box sits on a triangle of land between railway tracks, making access challenging. Andy said: “So many boxes are so close to the track that you need possession of the line. Here, constructing the scaffolding was more difficult as there was a certain amount of safety work in getting the material on and off the site, but once it was up you could carry on regardless, as the box is several metres away from the tracks.”

Television presenter Tim Dunn outside Severn Bridge Junction, daytime
Television presenter Tim Dunn shows the signal box right in the middle of the tracks

Did you know?

You can tell which company built a signal box just by looking at it; each railway company had its own distinct design.

Severn Bridge Junction Box, built in the early years of the 20th century is a standard London & North Western Railway design, “although it is absolutely huge” says Andy.

He said: “The L&NWR boxes had a characteristic brick-base with a wooden upper part and gable ends: if you look at the boxes along the North Wales coast … most places had basically the same design, although they are much, much smaller.”

Read more:

Step back in time… and inside Britain’s busiest signal box

Why the end of the gauge war didn’t standardise Britain’s railway

Our signalling heritage

What happens to signal boxes when they retire?

The Network Rail archive

Our history