Along with principal contractor AmcoGiffen, engineers will assess the condition and strength of the viaduct, while carrying out work to protect it from water erosion, completing concrete repairs and making improvements beneath the track to keep the stone ballast in place.

It’s part of Network Rail’s ongoing maintenance programme and will help futureproof the landmark, which sits 100ft above the River Finnan on the West Highland Line, 17 miles from Fort William. The work is scheduled to take just under a year to complete.

There will be no disruption to rail services during the work and no change to the appearance of the structure – the longest concrete viaduct in Scotland (spanning 1000ft) - when complete.

Laura Craig, scheme project manager, Network Rail, said: “The viaduct is an iconic landmark which attracts visitors from across the world, so we’ve worked hard to develop a solution which will help preserve the structure, respect its historic significance while minimising the visual impact of our work.”

Stephen Campbell, operations director, AmcoGiffen, said: “We are privileged to contribute to the preservation of this cherished landmark and will work closely with Network Rail to protect the heritage of the viaduct and surrounding area while repairing its structural integrity for generations to come.”

Mark Ilderton, service delivery director, ScotRail, said: “ScotRail journeys on the West Highland Line, taking in the iconic Glenfinnan viaduct, are incredibly popular and it is fantastic to see this work being carried out by our colleagues at Network Rail Scotland.

“There will be no disruption to any of our services during the work, and we look forward to giving as many people as possible the chance to experience the journey in the coming weeks and months.”

Network Rail is working with Highland Council, the landowners and stakeholders to make sure work is carried out as sensitively as possible. This includes using carefully selected stone for the repairs that match the existing masonry.

Councillor Ken Gowans, chair of The Highland Council’s economy and infrastructure committee, said: “The scenic rail journey has become a hugely popular route between Fort William and Mallaig. It is very popular with Harry Potter fans and attracts visitors from across the world. In addition, it also provides a valued service to those living and working in the communities it passes through, so it is essential that repair works and works to safeguard the routes future is carried out.”

Residents and businesses operating near Glenfinnan will receive letters outlining the planned work programme and be kept informed of progress. Community drop-ins are also being planned and more information will be made available on these in due course.