What's the difference between a twitcher and a gricer? Answer: not much. One spots birds and the other spots trains. Unfortunately there's not an imminent prospect of sighting either from where I'm sitting amid the May blossom on the platform at Salhouse station, on the remote Bittern Line in North Norfolk.
The small, heron-like bird that gives the line its name is one of the shyest and rarest in Britain. And trains are not too plentiful hereabouts either, since the infamous Dr Beeching came along in the 1960s and cut a swathe through the rural railways of East Anglia.
But we must be thankful that the trains have not entirely disappeared from this charming branch line survivor of a golden railway age. Running for 30 miles from Norwich through the Broads to the north Norfolk seaside town of Sheringham, the Bittern Line offers many things – ancient landscapes, historic houses and churches, ravishing vistas across wetlands and pretty Victorian seaside resorts.
I'd been commissioned to spend a two-year odyssey aboard the slow trains of Britain to rediscover the pleasures of our remaining branch lines as the 50th anniversary of the Beeching cuts approaches.
Without doubt, the Bittern Line is one of the loveliest and most unspoilt of them all. How many other railways in Europe link a medieval city, a national park and an area of outstanding natural beauty, along with some of the nation's most unspoilt seaside resorts, over such a brief distance?
There was a jolly carnival atmosphere earlier that afternoon, as we rattled north over the points out of Norwich Thorpe station. Arthur, the conductor, explained that these were people from Norwich, travelling down to Cromer for the annual Crab and Lobster Festival on the coast. Lucky old Cromer, since the weather for this particular Whitsun weekend is uncharacteristically hot. Half a century ago Philip Larkin wrote Whitsun Weddings, one of the most famous railway poems of all, as he took a journey on a similarly warm afternoon out of Hull, where he was the university's librarian. "All windows down, all cushions hot," he wrote, as his train pulled through the eastern counties.
Today the seats are hot, but our train has neither air conditioning, nor, as in Larkin's day, those old-fashioned windows with leather straps that would drop down to let in a waft of spring air. But the views are magnificent as we climb past the Norwich fringes and into open countryside, with the froth of cherry blossom everywhere. Overgrown lineside vegetation whips against the side of the train as it passes through dreamy wayside stations, where much of the time, in the words of Flanders and Swann's famous song Slow Train, "no-one departs and no-one arrives".
At Salhouse, the first stop out of Norwich, not much remains except memories. One of the brick station buildings survives, with cheery Victorian cast iron spandrels supporting the canopy, but the waiting room and the cubby hole, where porters supped their tea, is now boarded up – although someone has taken the trouble to fill the platform tubs with violas.
As we head down the gradient to Hoveton & Wroxham, a pair of red admiral butterflies bump against the window and a hare kicks its heels away from the train. Sheep form little white dots across the landscape as far as the eye can see – in a view which is otherwise empty apart from the tall, graceful towers of churches created by the prosperity of the wool trade. Soon we are at the woollen capital of Worstead, where weavers from Flanders first spun the famous worsted cloth in the 12th century.
But don't alight here hoping to take some home with you. It hasn't been made here for more than a century. The last weaver John Cubitt died in 1882 aged 91.
There is no mistaking the approach to Cromer. The tower of the church of St Peter and St Paul soars over the town and, at 160 feet, is the tallest in Norfolk. In the minds of railway enthusiasts, Cromer station has a similarly exalted status as only one of three surviving on the national network from the days of the fabled Midland & Great Northern Railway. When they shut most of 183-mile network of the "Muddle & Get Nowhere" in 1959, it was the biggest single railway closure yet seen in Britain and since then the railway has acquired an almost mythical status – hard to appreciate unless you can understand that curious cocktail of nostalgia, sentiment and overwhelming sense of loss that fuels railway enthusiasm.
These days, to most people's eyes, Cromer station is a melancholy place – just a single platform with a bus shelter and a disused signal box. I head for the exit, where there's a sign saying "Welcome to Cromer, Gem of the Norfolk Coast" – and a gem, if such a word has any meaning in the cliché book of tourism, it turns out to be.
Not much seems to have changed since it was described in Jane Austen's Emma as "the best of all sea bathing places". Neatly-groomed waiters lounge at the entrance to the Hotel de Paris, high above the pier, its wallflower-red sandstone frontage now heavily worn by more than a century of spray. Old ladies toddle in on walking sticks for afternoon tea, as they have done for more than a century – when it was the seafront residence of Lord Suffield – and Edward VII would slip in a side entrance for a spot of recreation with Lily Langtry. "Stephen Fry was once a waiter here," one of them tells me proudly. "He looked lovely in his uniform."
Could there be a jollier spring afternoon at the English seaside than today? Small boys jostle each other as they cast for crabs off the pier, while the mayors of Cromer and Sheringham rattle their chains, as they prepare to present awards for the most impressive catch.
Tonight at the Pier Theatre Joe Brown "of Joe Brown and the Bruvvers, the famous 1960s rock group" is playing. On the seafront, an elderly fisherman flashes arthritic fingers to weave a crab trap.
"Just call me Speedy," he says. "Doesn't half make your fingers sore when the wife asks you to do the washing-up afterwards."
As the sun starts to set and the ice cream sellers pack up, the trains in the timetable are few and far between, so I decide to walk along the coast to my destination for the night – the old Midland & Great Northern Railway's hotel at West Runton, the last station along the line before Sheringham. The M&GN may not have had much of a talent for running railways, but it spotted an opportunity for redeveloping a coastline of fishing villages marooned in the middle ages into what it hoped would be a playground for its clients – the weary miners and hosiery workers of the East Midlands.
I am hot and hungry when I book into the hotel, which sits next to the single platform station – a grand and rather elegant dowager with make-up fading (the gilded letter "O" from the hotel name hasfallen off the façade). It was while staying here, recovering from enteric fever, that Arthur Conan-Doyle had the idea for his mystery Hound of the Baskervilles, drawing on the ghostly legend of Black Shuck – the "hell hound" of Norfolk, which was said to have roamed the lanes along the coast. The ivy-clad gothic façade of nearby Cromer Hall is said to have been the model for Baskerville Hall. How did the story get translated to Dartmoor? Who knows? But visible from my bedroom window is Beacon Hill – at 338 feet, the highest point in Norfolk. No dramatic West Country moor, certainly, but dramatic enough and a rebuttal to the great myth about the county perpetuated by Noël Coward in his play Brief Encounter: "Very flat, Norfolk."
There's more drama still to be had in tiny West Runton, as I head hungrily for the only pub in the village.
"No food tonight, mate," says the young barman. "But it was a bit different here in the old days," he tells me, as I settle for a packet of salt 'n' vinegar crisps and half a pint of Adnam's.
"Can you believe the Sex Pistols played here once? And T-Rex, The Clash, the Boomtown Rats, King Crimson, Thin Lizzy, Blue Oyster Cult..." He reels off a fantasy playlist of punk rock bands from the Seventies. It turns out that this was the site of the legendary West Runton Pavilion, a former dance hall converted to an off-the-beaten-track venue for groups to test out their UK tours. The idea was that the remoteness made it inaccessible to sneery metropolitan music journalists. Even Chuck Berry played here before the pavilion was demolished in 1986.
But who will ever know whether the Father of Rock arrived on the tracks of the M&GN, or if this sleepy Norfolk village once reverberated to his famous song "Downbound Train": The passengers were mostly a motley crew/Some were foreigners and others he knew/Rich men in broadcloth, beggars in rags/Handsome young ladies and wicked old hags...
Surely he cannot have been referring to the ladies of the West Runton and District Womens' Institute, who are busy watering the station garden as I arrive to catch the early train to Sheringham next morning.
The ladies have "adopted" the station and turned the site of the demolished buildings into a kind of paradise garden – a riot of early summer bloom, with roses tumbling over a pergola.
"I've known this station since I was a girl," one of them tells me. "Here, where the geraniums are, was once the stationmaster's house. It used to be full of life and we keep the site alive to this day. We love this place."
"The rail operators tangle with these ladies at their peril," says a man aboard the train. "They are the most ferocious guardians of the line. If another Beeching ever came along here, I wouldn't fancy his chances!"
'On the Slow Train Again: Twelve More Great British Railway Journeys' by Michael Williams, is published this week by Preface, price £14.99
Travel essentials: The Bittern Line
* The Bittern Line runs from Norwich to Sheringham (08457 484950; bitternline.com). The first train leaves Norwich at 5.20am and Sheringham at 6.32am, running roughly every hour until 10.45pm. The journey lasts approximately one hour.
* The Links Country Park Hotel, West Runton (01263 838383; links-hotel.co.uk). Doubles start at £65, including breakfast.
* The Cromer and Sheringham Crab & Lobster Festival runs from 20-22 May (07796 463507; crabandlobsterfestival.co.uk).
* Visit North Norfolk: 0871 200 3071; visitnorthnorfolk.com