The route, stretching from Inverness to Wick and Thurso, is a vital connection for local people and tourists.

The £11.5 million investment included refurbishing a five-mile section of track between Brora and Helmsdale, some of which dated back almost a century, as well as replacing nearly nine miles of ageing rail between Invergordon and Fearn.

The work will deliver smoother journeys, reduce the risk of delays, and extend the lifespan of the infrastructure.

Scott McMurchie, scheme project manager at Network Rail, said: “The Far North Line is such an important transport link for many communities in the Highlands, and this investment will help ensure it continues to serve passengers safely and reliably.  

“The project was a significant undertaking, involving complex engineering in a remote and challenging environment. Closing the line for the duration was essential, ensuring the safety of our teams and the public, while minimising the length of disruption.

“We’re grateful to residents and businesses for their patience and support and know they’ll continue to benefit from this significantly improved route for decades to come.”

A team of specialist engineers carried out the work using traditional track-laying techniques, changing around 2,500 sleepers and installing around 3.75 miles of new rails.

Drainage improvements and new ballast also enhance the line’s resilience to extreme weather and give passengers a more comfortable journey.

Over the three-week closure, a total of 6,720 hours were worked by Network Rail staff on a 24/7 shift pattern.

Replacement bus services were provided throughout the line closure to help keep passengers moving.

Mark Ilderton, ScotRail service delivery director, said: “We’re pleased to welcome customers back to the Far North Line following this major upgrade.

“The work carried out by Network Rail will make a real difference to the long-term reliability of services, which are a lifeline for communities across the north Highlands. 

“Our priority throughout the work was to keep people moving, and we’re grateful to customers for their understanding and patience while these improvements were delivered.” 

During the works, Network Rail staff also took part in 49 hours of volunteering in the local community, including making new planters from old railway sleepers for Brora station platforms, and holding STEM and ecology talks at Brora Youth Group and Golspie High School.

Ian Budd, convener of Friends of the Far North Line, added: “This route is vital for the social and economic wellbeing of the Highlands. It connects people to jobs, education, healthcare, and tourism.

“We’re delighted to see this much-needed investment and are optimistic that this 150-year-old line’s importance will now attract further development so it can thrive for another 150 years.”