Last station: Gunnislake

Devon and Cornwall have some glorious railways, such as the elegant, lazy arc carved around St Michael's Bay by the Penzance train, and the coast-embracing line from Teignmouth to Dawlish. But the real aficionado is travelling on one of the shorter, stubbier stretches.

There are two ways to travel to Cornwall by train, and the thousands of holidaymakers rumbling across Brunel's strident Royal Albert Bridge aboard InterCity 125s have chosen the lesser option. Seekers of scenery, railway history and solitude choose the Tamar Valley line.

Quite how this 14-mile zig-zag of track has survived round after round of railway cutbacks is hard to explain. On the day last week when I travelled on it, we passengers played out a 2-2 draw with the crew. Even at the frightful cost of 27 pence a mile I was paying, it is hard to see how Regional Railways can keep the line going.

Yet six days a week (and on summer Sundays), a two-coach train sets off from Plymouth to explore the river valley that divides Devon from Cornwall. You plod through the sorry cityscapes punctuated by pauses at Dockyard and Devonport, through stations whose antiquated names are sometimes longer than the platform needed for these two-coach shuttles: St Budeaux Victoria Road takes its place with Lympstone Commando among the more ambitiously named Devonian stations.

Your train diverts from the line leading across the Tamar here, and immediately the tone changes. The austere suburbs give way to grand views across to Cornwall - a collage of steeply wooded slopes sliding into sharp, black water.

In its promotional material, the railway company erroneously describes it as "One of England's loveliest branch lines". Yet only the last short segment was originally a branch. The stretch as far as Bere Alston, a truly heroic link between Plymouth and London, was built by the London & South Western Railway. Bere Alston was Devon's own Clapham Junction, where the Gunnislake branch darted off from the imperious main line. "Up trains" to London wheezed uphill towards Tavistock and skirted around the northern fringe of Dartmoor to reach the capital. Now the sole purpose of the station is as a reversing point, from which the train sets off to cross the Tamar into Cornwall.

Calstock could be the epicentre of the heritage industry, its sturdy cottages simpering prettily beneath the arm of a mathematically exact viaduct across the river. That the first village in Cornwall manages to elude the twee in favour of the Newtonian perfection of the viaduct is evident to everyone except passengers. Your pounds 3.80 ticket entitles you to get off, look around and wait two hours for the next train.

The last two miles along the Gunnislake branch climbs several hundred feet into the Cornish hills. The train hauls itself into a station which is more municipal car park than great railway terminus. We passengers alight, leaving Regional Railways pounds 7.60 better off - but us tourists much the richer.