There is a moment while travelling on the West Highland Line from Fort William to Mallaig when I can’t quite believe that the view from this train is real.

We’re on the stretch of the line from Glenfinnan to Mallaig, just as a break in the mountains reveals the white sandy beaches and blue sea beyond. It’s almost too beautiful for words.

I suppose I knew the scenery on this trip was going to be pretty amazing. After all, it is a global rail travel icon, up there with the Trans Siberian and South Africa’s Blue Train. It has been voted the world’s greatest rail journey on many occasions and had particular good fortune when one of its key landmarks was used in a series of films about a certain boy wizard.

Despite what you think you know about this historic line, however, the reality of seeing landscape this big and this bonnie – sometimes overbearing and haunting – from the comfort of a very ordinary train is something else. It has to be experienced to be believed.

Travelling by train is a different experience to driving, of course. As the train chugs up mountains you can’t help but think about the sheer achievement of building this line in the first place. What the Victorians did for us indeed. Some freight is carried on this line, but the most significant cargo is the 450,000 passengers a year, the vast majority of whom are tourists, many from outside the UK.

Another quite wonderful thing about this journey is that it takes you to places where you can enjoy some of the best quality seafood, game and meat you’ll find anywhere in the world; it’s a trip for foodies just as much for scenery buffs.

But more of that later. For now, let’s go back to the start of this epic journey, in Glasgow. There are actually two branches to this line, of course, one that goes to Oban, the other to Mallaig; my travelling companion and I are lucky enough to be doing both.

The three Scotrail carriages that take us north are serviceable, if a little tired. The train is packed when we leave on a Friday morning and there’s not much room for luggage. Train operator ScotRail Abellio plans to replace the rolling stock with improved trains over the coming months, offering more luggage room, improved comfort, catering and viewing opportunities – and wi-fi. All this will be most welcome.

The three and a half hour journey to Oban is the perfect overture to a world-class rail journey. Within just half an hour the urban sprawl of Glasgow is behind us, replaced by the tranquillity of the lush glens and pleasant hills around Helensburgh and Loch Long. Before long we’re coasting northwards through the familiar beauty of Loch Lomond, then the line divides at Crianlarich. From there it’s on to the grandeur of Loch Awe and Ben Cruachan, along the banks of Loch Etive towards the sea, past the Falls of Lora towards Oban itself.

It’s a few years since I’ve been to Oban, and in that time this busy coastal town appears to have become more bustling than ever. We walk round the crescent-shaped bay, marvelling at the views across to nearby Kerrera and further out to Mull. The CalMac ferries taking folk to the islands are busy, as are the many seafront restaurants, cafes and independent shops that populate the harbour and the town centre. As you watch the catches being brought in and going straight to the restaurants, you realise seafood really doesn’t get any fresher than this (as the bloke from MasterChef would probably say).

We eat that evening at the Waterfront Fish House, a busy modern restaurant overlooking the bay on the south pier. The Loch Awe trout fillet is the best I’ve had in years, beautifully cooked and accompanied by shrimp butter and celeriac puree. The views across the bay are equally spectacular.

After a pleasant night in the Dungallan House Hotel, next morning we say farewell to Oban and get back on the train, doubling back on ourselves until Crianlarich before heading northwards. As the scenery becomes more dramatic, you can start to feel the train changing gear and heading uphill. It’s this part of the line that provides one of the most memorable and arresting parts of the journey, through the bleak beauty of Rannoch Moor. We stop at Corrour, the highest station in the UK, which gained cult fame with its cameo appearance in the film Trainspotting. It’s then 50 minutes into Fort William, with menacing mountains as far as the eye can see. It’s something of a relief to get off the train and see some humanity as the train pulls into the highland town.

We check into our room at the Lime Tree boutique hotel, before heading out to the Crannog, the town’s most celebrated seafood restaurant, which sits on a jetty overlooking Loch Linnhe. This eaterie has been feted for 25 years and on tonight’s visit the reputation is deserved; the generous portion of local langoustines drenched in herb butter is simply exquisite. I’ve always thought langoustines the kings of shellfish – even tastier than lobster – and rejoice that we happen to have the sweetest examples in the world off our west coast. What a stroke of luck. It is no wonder our continental cousins put such a high value on these “prawns” and a disappointment that we don’t see more of them on more menus in Scottish towns and cities.

We’re up and back on the train early next morning. This is the section of the journey I’ve been looking forward to most, and the gods reward us with a sunny day to savour the journey north to Mallaig. It certainly doesn’t disappoint. It’s hard to overstate the magnificence of this stretch of railway. Like the Rannoch Moor stretch, there are mountains wherever you look but the scenery here is more lush and varied; the effect is less haunting, but perhaps more awe-inspiring. Of course, the icing on the cake is a trip across the world famous Glenfinnan viaduct – aka the Harry Potter bridge – one of the most iconic pieces of Scottish engineering of all time. It’s a wonderful moment, as all the passengers – most of them foreign tourists – get hugely excited and bring out the cameras, phones and tablets of every conceivable quality and size to catch it for posterity. Even the train conductor joins in, telling the driver to slow down and advising on the best views from the train.

On arrival in Mallaig, we find a taxi and head straight for one of my most favourite places, the beach at Camusdarach, just a couple of miles along the coast. This huge stretch of powdery white sand is framed by shimmering pale blue water and offers views across to Skye, Eigg, Muck and Rum. There is surely no greater pleasure on a sunny day than clambering up the rocks at Camusdarach, feeling the wind in your hair and looking out into the great Atlantic expanse beyond.

We head back to Mallaig, which is the end of line as far as this epic train journey is concerned. But it also marks the start of a new journey, this time by ferry, over to Skye. It’s just a short hop from Mallaig to Armadale, which sits on the stunning Sleat peninsula, and we have a treat in store: a night at Kinloch Lodge, the hotel and restaurant owned by food writer Lady Claire MacDonald and her family.

Attention to detail is everything at Kinloch Lodge, and nowhere is this more evident than in the Michelin-starred restaurant run by Marcello Tully. The five-course menu we eat from is impeccable, showcasing local seafood, game and meat with style and precision. The Mallaig hake given Tully’s “Indian” treatment is a wonderfully aromatic yet subtle triumph, while the crusted local lamb is tender and flavoursome beyond belief, treated by the cooks with absolute respect.

The hotel itself, meanwhile, is a warm, cosy delight of a place, quietly luxurious and never over the top. One thing’s for sure – it’s worth going to the end of the line and beyond for. Before leaving Skye we spend the following morning exploring Sleat on foot, revelling in its tranquillity.

By the afternoon we’re back on the train in Mallaig, settling in for the five and a half hour journey back to Glasgow. Some of the views seem different on the way back – weather conditions, time of day and your own emotions all play their part.

When we eventually roll into Glasgow it feels slightly odd to see an expansive cityscape from the window with its houses and streetlights – we’ve grown used to seeing mountains and glens. The end of this shared experience has come and the passengers wave each other off, knowing we’ve just shared something genuinely special. Is this the world’s greatest rail journey? Of course it is.

Marianne Taylor and guest travelled on the West Highland Line courtesy of ScotRail. For prices and train times visit scotrail.co.uk.

She stayed at the Dungallan House Hotel in Oban (dungallanhotel-oban.co.uk, 01631 563799), the Lime Tree Hotel in Fort William (limetreefortwilliam.co.uk 01397 701806) and Kinloch Lodge on Skye (kinloch-lodge.co.uk, 01471 833333).