Simon Calder: Welcome to Gatwick. Now get lost

The man who pays his way

"Of the 35 million passengers using Gatwick each year, 14 million arrive or depart by rail – making it the busiest airport station in Britain." So says Gatwick's chief executive Stewart Wingate. Compared with its rivals, the Sussex airport is superbly connected by train. Fifteen services an hour depart to London during the average day. But as many festive travellers know to their cost, Yuletide is far from average.

Pity the poor traveller who mistakenly lands at Gatwick around 9pm on 24 December, hoping to head for the capital by train. Unlike Amsterdam, Paris, Frankfurt and other leading Continental airports, rail services cease halfway through the evening of Christmas Eve. Trains start up again on Boxing Day.

Or do they?

Pity the poor traveller who mistakenly lands at Gatwick around 9am on 26 December, hoping to head for the capital by train. The good news is that cheery staff will sell you a one-way ticket for a reasonable £8.90, less than half the going rate on the festively suspended Gatwick Express –the main line is closed, as part of a nine-day blockage of one of the nation's most important rail corridors. But unlike the usual half-hour run to London, the journey to the capital is scheduled to take well over an hour – and begins by heading away from London. On a bus.

The railway industry says: "The vast majority of people expected to travel by train over the Christmas and New Year period should experience no disruption." The two-fifths of Gatwick airline passengers who use trains will, though. They will see a side of Sussex normally hidden from the traveller, on a journey I traced out on a chilly December morning.

Like the Orient Express, it is a journey to be savoured, not rushed. The trip begins with eastern promise: heading east-south-east to East Grinstead, taking a relaxing 25 minutes to cover eight miles. While the A264 may not be in the same league as California Route 1, it rolls through low hills draped in woodland that is on a one-way mission from deep green to gold.

A circuit of East Grinstead's one-way system brings you down to (a) Earth and (b) the railway station. Platform 2 is rather further away from the capital than when you began some time ago.

The average luggage-burdened traveller will board the waiting train to London Bridge. But for anyone unencumbered, the footbridge over the tracks marks the start of the Worth Way – a seven-mile arc along a former railway line.

Worth: a detour

The defunct track to Three Bridges cuts through sublime rural landscapes, populated by dog-walkers and the odd cyclist and doused with winter's magic. As the breeze ruffles the leaves that have fallen, and those still hanging on in the teeth of winter, you would not imagine that the world's busiest-single runway airport is but a few miles from the Worth Way.

Embers of a pale December sun filter through thinning trees to bestow an Impressionistic frisson on the northern fringes of Sussex – and remind you of the joyful turning of the seasons.

Halfway along, the Worth Way is interrupted by an estate of "executive homes" to eradicate any chance of resuscitating the Beeching'd line.The hazy rural bliss soon resumes, along a track now embroidered with stout Victorian bridges and tunnels. It culminates in the flinty glory of Worth Church – built when the Saxons, who gave Sussex its name were in charge.

It's downhill from here to Three Bridges station. By 27 December, this modest junction will be on the schedule of more confused Gatwick new arrivals. The cunning plan is to augment the East Grinstead connection with trains that run south from the airport towards Brighton. They swerve west onto the Trans-Crawley Railway through the sprawling New Town to Horsham. Here, the train reverses and finally chugs off in the general direction of London, ushering passengers beneath the shadow of Box Hill – high point of last summer's Olympic Road Race for cyclists. The train sets no records, taking 95 minutes to reach London.

Take the Orient line

After testing both the eastern and western diversions, I urge you to stick with the Orient. East Grinstead is the closest station to A A Milne territory, and the line north threads through a land of meadows, hedgerows, hills and valleys, with storybook names to match. After gliding past Crab Orchard Wood, you arrive at Dormans Station – on Blackberry Lane, just at the foot of Mutton Hill.

To remind you this is the most crowded corner of a densely packed nation, Morrison's car park at Oxted station is followed by a traverse of the M25. But scenery soon returns as you wend lyrically from Woldingham to Upper Warlingham. You cross the Greater London boundary with the windows still framing gentle farmland.

Even when the suburbs begin to crowd in, this trajectory is surely the most scenic of any railway into London: flanking a deep, narrow valley that would not be out of place in Bavaria. Coincidentally, the journey through the coy glories of southern England has lasted as long as it takes to fly from Munich to Gatwick.

The train operators to the Sussex airport are at least making an effort to run a Boxing Day service. The Heathrow Express is suspended on both 25 and 26 December, as are trains serving Manchester airport. Which is a shame, because the only form of long-distance transport running in Britain on Christmas Day that I can identify is a pair of BA flights, shuttling between Heathrow and Manchester.