The incredible train journey that starts in UK city and ends up in beautiful seaside town

The tiny, boxy sprinter train was parked at Mallaig station and was due to leave in five minutes, but we were still sitting in a cafe sipping our coffees.

A lapse in concentration after walking four days through Britain's last wilderness, from Glenfinnan to Inverie, had left the timetable's '3' looking like an '8'.

A moment of clarity to check the time and we were out the door, our steaming hot drinks left on the table, running for the station. We made it within a whisker of departure, much to the delight of the short and stout moustachioed conductor.

For the next five and a half hours, the West Highland line would take us through some of Scotland's most jaw-dropping natural landscapes and scenery, nailbiting hairpin bends, and a route like no other.

Out the window, we couldn't believe our eyes: a kaleidoscope of mountains growing and shrinking, disappearing over the horizon before popping from the ground like a grassy Jack-in-the-box. The trip is surely something everyone must experience at least once in their life — and at a little more than £20 for a standard ticket, is one of more the affordable bucket-list trips.

While our journey began in Mallaig, the easiest way to do the route is to begin in Glasgow, Scotland's second city, which is fairly easy to get to from almost every part of Britain.

Put simply the journey is the UK's most scenic: you leave the industrial glow of Glasgow and skirt along the ancient River Clyde, pushing on north for hours and into the wild depths of western Scotland.

It's hard to nail down a specific highlight on this route, but Loch Lomond and the Trossachs National Park, the Rannoch Moor with its roaming wild red deer, Glenfinnan Viaduct and the port of Mallaig are but a few of the hidden gems it has to offer.

You'll also meet a motley crew of characters jumping on and off the train, largely made up of hikers and amblers, each with a different tale.

Jackie, a 62-year-old Glaswegian, told of how she made the trip every year for the sheer joy of it. "It just never gets old, does it?" she said, a Cheshire Cat grin smacked across her face. I found it hard to disagree.

It doesn't take long to get out of Glasgow and the bustle of urban life, maybe 20 minutes or so, and soon the country opens up.

A diversion in the line at Crianlarich sends some revellers further north while others towards Mallaig.

It's at this point that the mountains come into play, with the towering Ben Lui to your left, and the mighty Ben More to your right. There's no end of them, with the Bens — those 4000 feet above sea level — and the Munros — those above 3000 metres above sea level — scattered around as if someone's just dropped them there.

Before long, the train pulls up at the famous Fort William, today known as the town everyone stops at to climb Ben Nevis, originally the first fort to be built in the region way back in 1698.

By 1745, it became fabled for its tough defence system after withstanding a brutal siege during the Jacobite rebellion and was after that used as a base for the hunt of Bonnie Prince Charlie. All of this natural beauty and history and yet the train hasn't even hit its best part.

Just up the road from Fort William is Glenfinnan Viaduct, made famous by Harry Potter and the Chamber of Secrets, which sees the old steamer cross its arches like something out of a period drama. 

Its tracks aren't exclusively used by the steamer, however, and the Scotrail passenger service chugs across the viaduct with views out to the stunning Loch Shiel and Sgùrr Ghiubhasachain. There was a glint of disappointment in the eyes of the keen tourists below hoping to get a snap of the Harry Potter train. Perhaps it never came that day. 

From Glenfinnan, the train pushes west, right out onto the coast and towards the Sea of the Hebrides, before arriving at the old port town of Mallaig.

There's plenty of time till the train makes its return journey — with departures every few hours — so the chance to explore the town, try some of its tasty seafood, and perhaps walk some of its trails is definitely on the cards.

Everyone's hungry by the time they reach Mallaig, regardless of the onboard catering. The no-frills Jac-O-bites Cafe offers a hearty meal, good tea and coffee, and good service, while the Central House offers those who want something a little stronger a great reprieve.

The majestic Isle of Skye can be seen across the strait, with its 12 seriously difficult-to-climb Munros visible for miles around.

It's a world-beating journey, in a world-beating part of the globe, with a world-beating cast of characters on board — just make sure you triple-check the timetable before you spend a little too much time over that last cup of coffee.

A one-ticket can cost as little as £10 with a railcard, while journeys booked a few days in advance can be had for £22.