The UK's highest railway owned by a leading Scottish Government economic development agency is set to be shut for at least a year as new problems dog the beleaguered structure.

Concerns have previously been raised about the future of the Cairngorm railway after it was shut on August 25 and after a series of false dawns, was shut for an indefinite period and has not been available for the winter season.

Now it has emerged that a programme of remedial works is to enter a new phase and is likely to take months to complete.

It has been confirmed that there is an aim to have it back in service for the start of the snow sports season in December.

Calls have previously been made for a public inquiry after it was confirmed that safety issues were continuing to dog the UK's highest railway, which was taken out of service initially to deal with a series of 'snagging' works which meant it was due back in action at the start of September. But eight months later, it remains out of action.

The development has become a familiar theme for the key facility for the Cairngorms, a major Scottish tourism attraction and centre for recreation with downhill hillwalking and rock climbing a major draw for the 1.92m who visit the national park every year from around the world.

READ MORE: Payout in Scot gov agency court fight over Cairngorm rail costs

The crucial funicular, which was opened in 2001 and connects a base station with a restaurant and a ski area 1,097m (3,599ft) up Cairn Gorm mountain near Aviemore, was closed in September 2018 due to structural issues.

Owner, the Scottish Government's Highland and Islands Enterprise agency had at one point included a provision of £14.3m for the cost of reinstating the funicular which had been expected to take two years.

But the costs of the troubled railway have ended up costing nearly three-and-a-half times the original estimate.

The Herald:

The urgent repairs rose by a third from £16m to £21.5m.

The faults were discovered after the costs of building the funicular spiralled from £14.8m to £26.75m.

According to the Cairngorm National Park Authority strengthening works after issues to the railway viaduct had emerged five years ago, involved reinforcing props and concrete bases beside 63 out of 94 piers.

It finally came back into action in January after a four-year hiatus - but then promptly closed "temporarily" nine months later.

Eleven days after the works were hoped to be completed "relatively quickly" at the end of August but on September 6, it emerged that it would not be back up and running until the end of the month.

The agency later said the scale and complexity of the project, which includes continuous testing to ensure public safety, had led it to revise its schedule to complete the job to mid-October.

In mid-October, HIE said the works to resolve the issues would have to continue into November and apologised to visitors.

Then the railway was not expected to be ready for the start of the Cairngorm season on December 22 and its return to action was classed as indefinite.

Now HIE and Balfour Beatty say that a new phase of a programme of remedial works has begun.

Multiple teams from contractor Balfour Beatty, appointed by Cairngorm Estate owner Highlands and Islands Enterprise (HIE), are to be deployed on the mountainside.

They say a prime area of focus will be hundreds of ‘scarf joints’ linking beams and piers along the 1.7km viaduct These were installed as part of a major reinstatement programme that ran for just over two years from November 2020.

In addition, testing is under way on tensioning works to beams and diaphragms that were also installed as part of the reinstatement programme and remedial action will be taken as required.

Hector MacAulay, managing director of Balfour Beatty’s Regional business in Scotland, said: “We are working hard to complete this programme of remedial works as quickly as possible, deploying multiple teams simultaneously to safely reinstate this unique attraction and resume service before the next winter snowsports season.”

Activists who have been following the state of the railway were expected to take the matter to the transport minister Fiona Hyslop asking her to reconsider the safety of the funicular before it is re-opened.

One said that it was right to keep the funicular closed until safety issues were resolved but added: "It is horrifying that after all that has already happened, we are in a position that it will remain shut for a year or more. There should be an inquiry into what is going on."

Highlands and Islands MSP Edward Mountain said users of the Cairngorms and businesses who depend on them deserved clearer answers.

“A public inquiry into this mess has never been more essential.

“Despite the appointment of contractors, we still don’t know when the railway will reopen, how much it’s going to cost, or how it is all going to be paid for.

“I know businesses across the area are desperate to know when they can expect this important attraction – the only one of its type in Scotland – to properly function.

"We also need to know, having opened again last January after repairs, why a whole load of new repairs are required - HIE and the contractors seem to be making it up as they go along.”

The decision to close the railway came after the leading Scottish Government economic development agency settled a court action against constructors and designers over structural problems. HIE said that it had received £11m after settling the court action.

The Herald:

It had been pursuing a £14.5m claim against the company that owns Morrisons Construction and the civil and structural engineers for the scheme.

The agency made claims over defects in the design and construction of the railway and breaches of contracts that emerged after the funicular was forced to shut five years ago.

HIE said after it was forced to close the funicular again in August that a 12-month snagging and inspection programme has been running since the relaunch, "as is usual practice with complex engineering projects".

It later said the disruption followed an inspection that showed that some of the ‘scarf joint assemblies’ that link the beams at the top of the piers did not meet the required tension.

The viaduct is supported by 94 piers of varying heights, each one effectively a small bridge.

It ascends 450 metres up Cairn Gorm, with the track entering a 300m tunnel in its final stage leading into the top station.

News of the long-running case emerged in 2021 when it was revealed that ministers had to refund part of an EU grant for the original Cairngorm funicular because of discrepancies in the way it tendered for the work as costs spiralled.

Stuart Black, chief executive of Highlands and Islands Enterprise, said: “Balfour Beatty’s commitment to concluding these important works over the coming months is very welcome.

“This is still a challenging period for Cairngorm and we want to thank all the loyal supporters who continue to visit and enjoy all that the mountain estate has to offer throughout the year while work is ongoing to bring the funicular back.”

The funicular viaduct supports the railway that ascends Cairn Gorm to an altitude of over 1,000m.

Originally opened in 2001, it operates two carriages carrying visitors between the Cairngorm base station and Ptarmigan building, which houses a restaurant, shop, exhibition and viewing platform.

During winter, it is the main form of uplift to enable skiers and snowboarders to access higher parts of the mountain.

Cairngorm Mountain remains open while the programme of remedial works is under way.