IT was a trip my French friends had long dreamed of, planned and saved for, and a couple of weeks ago they finally took the West Highland Line, first from Glasgow to Oban, then on to Fort William and Mallaig.

It is, of course, hailed in glossy international travel guides as one of the world’s great railway journeys, made all the more iconic by the use of one of its key pieces of infrastructure, the Glenfinnan Viaduct, in the Harry Potter films.

Read more: Row over 10-day closure of West Highland Line

So, I asked my friends on their return, how was it? The word “magnifique” was used repeatedly to describe the scenery. And would you recommend it to your friends back home? The answer to this one, however, was an emphatic “non”.

Why? The trains, of course. Rickety, overcrowded, overbooked carriages, lack of luggage space, uncomfortable seats, catering that comprised of crisps and instant coffee, inadequate windows, overgrown trees making visibility difficult, service cancellations; their list of complaints was extensive. The rolling stock, they said incredulously, was little better than that used on the local network in Glasgow, despite the journey from Mallaig to Glasgow taking five and a half hours.

My heart sank. I’d tried to warn them that the trains would not be up to European standards, but they were aghast at the reality. “What a terrible waste of incredible landscape,” they kept saying. I was ashamed but couldn’t argue with a word of what they said. I’ve taken the West Highland Line three times in the last five years and had passenger experiences that range from not as bad as I’d feared, to bloody awful. The staff who work on the trains are pleasant and stoic, but the trains themselves are an embarrassing disgrace.

Greatest railway journey on earth? Hardly. That the landscape is breath-taking and spectacular isn’t in question. Glimpsing white sandy beaches and shimmering sea through the mountains on the approach to Mallaig is one of life’s great experiences. But when you’re assured a more comfortable ride with better visibility and catering on the local rail network in Munich, something is fundamentally amiss.

Read more: Row over 10-day closure of West Highland Line

To think that Scotland is letting its visitors down in this way, not to mention the communities that would see such economic benefit from a well-served West Highland Line, is frustrating and depressing in equal measure, especially since rail tourism, with its cleaner environmental footprint, is surely the future.

Not that the state of trains is putting tourists off. Indeed, the global trumpeting of Scotland means passenger numbers are rising on all branches of the line; Glenfinnan station saw a 27 per cent increase last year. Tourism has never been more valuable to the Scottish economy, bringing in upwards of £11bn a year, with visitors from Europe and the US flocking here off the back of a cheap pound and TV shows such as Outlander.

But the more visitors that come, the more ill-equipped ScotRail will be to give them a pleasant journey on the West Highland Line. Improvements have been promised many times over the years but come to nothing. A few extra services have been put on in summer, and some new carriages with better luggage space are apparently in the offing. But better trains with improved seating and windows, and locally-sourced catering, are still nowhere to be seen, despite being mooted after Abellio was given the rail franchise in October 2014.

To be fair, ScotRail can only work within the financial confines of its contract. And a painfully slow-moving Transport Scotland review of the line is charged only with exploring improvements within current levels of investment. It’s also worth pointing out that the line is old and remote, which limits the type of trains that could be run, and the Highlands has long been at the back of the queue when it comes to rail upgrades.

What’s needed now, then, is a far more ambitious improvement plan for the West Highland Line, one that includes infrastructure boosts for the communities along the way as well as fully-staffed, modern trains with viewing carriages, comfortable seating and a high-quality catering offering serving tasty local produce. In other words, the sort of trains that are the norm on scenic journeys in Germany, Switzerland and France. How did they get such trains? By making public transport and tourism a political priority.

If the political will existed in Scotland to raise the funds and bring stakeholders together, the West Coast Line could have the best trains in Europe. Are you listening, SNP Government? You can’t just blame ScotRail and Westminster - all need to work together for change.

Boris Johnson makes his first Prime Ministerial visit to Scotland today, fresh from backing a high-speed rail link between Leeds and Manchester. He could do worse than trying to win over his many detractors here by promising the Scottish Government the sort of funding that could transform our rail infrastructure. And first in the queue for investment should be the West Highland Line. Without it, this jewel in the crown of Scottish tourism can never be a truly great railway journey.