Slow travel begins before you board

The appeal of slow travel is simple: you arrive somewhere having actually seen the country in between. One railway runs for roughly 120 miles between Shrewsbury and Swansea, and it does exactly that. Four hours, more than thirty stations, a top speed that rarely troubles anyone, and a window that keeps handing you hills, estuaries, woodland and one or two viaducts worth putting your book down for.

It is often called the Heart of Wales line, and the name earns itself. Book a seat on a weekday morning in late spring or early autumn and you will have space to spread out, a table for a flask, and no particular reason to hurry.

What you will see from the window

The first stretch out of Shrewsbury is gentle — flat fields, the occasional heron, the sort of countryside you think you have seen before. Then the border arrives. Around Craven Arms and Knighton the land starts to fold, and by the time you are climbing towards Knucklas you are in proper hill country, with hedges close enough to the glass to count the leaves.

Mid-journey brings the best of it: high moorland, the long empty sweep above Llanwrtyd Wells, red kites turning over the ridges, and the Cynghordy viaduct — a curve of masonry over a wooded valley that has no business being as dramatic as it is. Further south the hills soften into farmland and the line follows the Tywi valley down towards Llandeilo, before the final run to Swansea and the wide flat brightness of the estuary.

Three stations worth getting off at

Half the pleasure is breaking the journey. All three of these have a walk within ten minutes of the platform and somewhere decent to eat.

• Knighton — a border town split between England and Wales, with the Offa's Dyke Path running through it. A short climb up to the dyke itself gives you a view back over the town and the viaduct, and the walk back down takes about forty minutes at a stroll.
• Llanwrtyd Wells — the smallest town in Britain and the high point of the line. Good walking straight from the station up onto the moor, and a couple of inns in the square doing generous sandwiches and a decent pint of local ale.
• Llandovery — a proper market town with a ruined castle, a river walk along the Bran, and a handful of cafés and pubs that do not mind muddy boots. It is an easy place to while away three hours before the next train south.

The practical bits

A few things are worth knowing before you set out, because this is a line that runs on its own terms.

• Many stations are request stops. If you want to get off, tell the guard when you board, or make it very clear you are standing up for your stop. If you are waiting to get on, put your arm out as the train approaches.
• Sundays are sparse. Some stations see two or three trains all day, and winter timetables are thinner still. Check the day's times before you commit to a long walk.
• There is no buffet. Take a flask, a bottle of water and something to eat. The scenery is better than any trolley anyway.
• Buy a flexible ticket if you can. The whole point is being able to change your mind at a request stop.
• Allow a full day for the end-to-end trip, or split it over two and stay overnight somewhere like Llandeilo.

Making a weekend of it

The line rewards an unhurried two days far more than a rushed one. Travel down on a Friday afternoon, stay somewhere small and slightly old-fashioned, and walk on the Saturday. Then take the train back on Sunday — or, if the Sunday service is too thin to trust, on Monday morning, which is quieter and cheaper anyway.

Pack light: a waterproof, boots or trainers with grip, a warm layer, and a paper timetable if you are the sort who likes not relying on a signal. Mobile coverage is patchy in the valleys, which is part of the charm until the moment it is not.

Why it is worth the extra hours

Nothing about this journey is efficient. That is the argument for it. You get four hours of Welsh border country at a pace that lets you notice it, a walk at the end, a pub lunch with a view of a hill you have just climbed, and the small satisfaction of arriving somewhere by a route most people have forgotten exists.

Take the slow train. Get off somewhere small. Order the pie.