Slate and steel to honey and rust in six hours flat: that is the miracle that, from next Friday, will transform travel. The most exciting aspect of the acceleration of Eurostar trains from London's revived St Pancras station is that, for the first time, travellers can go overland (and under water) from London to the Mediterranean in six hours. And the place, the only place, where you can achieve that "NW1 to southern sea" transition in 360 minutes is Marseilles – the 360 city, which celebrates the globe more than any other in France.
Mind you, the boffins who compile the timetables have not made the voyage especially easy: with no direct trains from London to Marseilles in prospect, you have to change trains along the way. After about six hours' worth of study of the timetables to and within France, I have identified just one journey a week on which the 360-minute trip is feasible: welcome to the 11.32am non-stop from St Pancras to Paris Gare du Nord. It runs only on Fridays, and is the only train that gets to the French capital with just enough time (striking public-transport workers permitting) for you to hop a couple of stations on the RER to Gare de Lyon, and board a non-stop train departing more or less immediatement to Marseilles.
No one has made that 360-minute journey yet, because it has not been possible; the present link from Waterloo to Paris is simply too slow. But over a series of trips I have covered almost all the ground, apart from the first stretch, and I have glimpsed enough of St Pancras to know how the trip will begin. The departure itself is triumphant, gliding out of the world's most magnificent shed. Even though the London skies may match the slate that gives St Pancras its elegance, the graceful steel arches of the Barlow Train Shed provide a suitably inspiring start, though the view is erased a minute later when the train dives into the London Tunnel. About seven minute you emerge into southern Essex, where the skies and suburbs unite in a grey smudge. At 186mph the view becomes a blur, which at least may avert a sense of disappointment among new arrivals to Britain.
Once across the Thames and on the existing high-speed line through Kent, prospects improve: the "Garden of England" provides a suitably verdant haze. And after the Channel tunnel, everything seems to grow by two-point-something: France occupies slightly more than double the area of Britain, with the same population. As a result, you get a sudden sense of space. The meadowlands peppered with pretty villages while the Picardy sky provides a screen playing out a meteorological drama.
Look, there goes Lille: the advantage of the train is that it brings you close to, but insulates you from, the clutter of industry and apartment blocks and autoroutes that define the city.
Now, the first rule of travel is that you should never merely change trains in the French capital; Paris is always worth more than a mass-transit move between stations. But the 360 trip demands that you forsake the views at Gare du Nord and dart down to the platforms for the RER suburban express that burrows beneath Paris. You have 33 minutes between the Eurostar's arrival from London and the TGV's departure to Marseilles from Gare de Lyon. If the RER arrives promptly for an eight-minute ride, grab a café crème at the gorgeous station brasserie, Le Train Bleu, before boarding le train gris à la mer bleue.
High-speed rail may still thrill you and me, but for the French it represents the everyday; for the past six years, covering 500 miles in three hours flat has been the norm. Sit back, relax and enjoy not flying. The journey south provides a study in changing light. Compare this with the flight, where you soar from gloomy Gatwick, piercing the cloud cover into unnaturally bright sunshine. How much more gratifying to soak up the softness of focus at ground level through the spine of France to the wayward and wonderful city that is the Queen of the South.
On the final approach to Marseilles, the driver has to start braking somewhere around Aix-en-Provence in order to reduce the velocity to zero by the time you reach St-Charles station. France's riposte to the engineering marvels of Barlow was Eiffel, who obliged Marseilles with this elegant, angular structure.
This city is France's window on the world, and – as with other great ports – the world has come to Marseilles. You could change here for ferries to Africa, but why bother? Morocco, Algeria and Tunisia have come here, bringing an ambience of exotica, excitement and energy. More of that in a day or two...
The gods of travel oblige more often than not, at least in France. Assuming the train from Paris takes the prescribed three hours, it is now 6.20pm, local time, and you have exactly 12 minutes remaining to dip a toe into the Med before that six-hour deadline. Don't panic: I have paced it out, and you can walk it in a brisk 10 minutes. Turn left out of the station and you find yourself at the top of a wide flight of steps, flanked by elaborate statues that celebrate the French colonies in Asia and Africa. At the foot, bear barely left along a broad avenue, the Boulevard d'Athènes. Five minutes from the platform, you reach what is most clearly the artery of Marseilles: La Canebière. Turn right and you can smell the sea. This is the grand approach u o to the Mediterranean that Louis XIV ordered in 1666; the Sun King's avenue to the sun. Five minutes later, you emerge at the Vieux Port, a gouge that brings the Mediterranean right into the city centre. Shoes off, perch on the flagstones that provide the moorings for hundreds of yachts, and dangle your feet into water, then watch the reflections of the city lights ripple away. Six hours ago, you were in London. Right now, you are in heaven, or at least a close approximation – and it gets even better.
Take in this scene, then resist the bids for your company from competing bars until you get to Le Bar de la Marine. Here, an glass of rosé with a cube of ice will set you back two-and-a-half euros while you are transported back two-and-a-half epoques. Carbon-dating the Marine bar is tricky, not least because there are columns and arches that appear Greek or Roman. But the curling iron staircase grew out of Art Nouveau, while the bar itself bears the mock-Egyptian hallmarks of Art Deco. The colours, though, are strictly those of Provence: terracotta, wheat, and a wash of duck-egg blue that is remarkably similar to the roof at St Pancras, filtered through a heat haze. Well, actually a smoke haze, with one or two customers contributing Gallic ambience to the atmosphere by puffing their way through Gitanes. Muse that, three centuries before the birth of Christ, Pytheas embarked on from the harbour on a voyage to the northern seas, charting Britain, the Baltic and Iceland.
After the aperitif, for the most satisfying conclusion to a dream journey you need to head for la plage. Not the nearest beach, the Plage des Catalans – it is fenced off for the winter – but the Restaurant la Plage close by, which is home to the best-value bouillabaisse in Marseilles. The hardest element of a seafood dinner in the south of France: pronouncing the name of the signature dish. "Bwee-yer-bess" did the trick (though read page three before you decide to take any linguistic advice from me), and cues a meal as theatrical as it is gastronomic.
First, a bowl of rich soup the colour of copper is brought to the table, together with grated cheese and croutons. While you sample it, a platter of fresh fruits de mer is presented for your inspection: moules, an array of fish and a reproachful-looking prawn. When you sign off your dinner-to-be, the chef turns the heat on, and the creatures undergo a recipe that is its name: quand ça bouille ... abaisse, or "when it boils, lower the heat". The soup is removed, and returns recharged with the seafood. Taste the Med in the moules, savour the magic of garlic sauce in bringing blander fish to life (no, not literally, silly), and leave le roi de la mer, the prawn, till last. Then, after eating the best of the ocean, fall asleep to the sound of it.
Dawn in Provence is mesmerising. The craggy shoreline slowly comes into focus. As the traffic noise increases, the sea begins to shimmer. The true colours of the south intensify: stone the shade of honey, roofs the tone of rust. By the time the sun has hoisted itself to the south-east, you can witness the same spectrum as, say, a maple forest in autumn. But this is a man-made city – the oldest in France. The original settlers were the Greeks, who created the area known as Le Panier. At the centre of this mainly car-free district is La Vielle Charité. This three-tiered courtyard with a domed church in the middle began life as an "enclosure of paupers". After serving as an army barracks, it faced demolition (echoes of St Pancras) before a champion saved it: the local architectural hero, Le Corbusier, more associated with the scarily modern. The complex now houses a restaurant and a museum to the art of Africa, Oceania and Amerindians.
Marseilles has spread, haphazardly, way beyond the Greek core to occupy every square inch of land and now drapes itself messily over every hill. It may have only one-third of the population of Paris, but it covers a far larger area. Happily, getting around has become a breeze in the past few months. First, the city's tram system came into operation, with cars excluded from some key streets to the benefit of everyone except taxi drivers. And last month a well-conceived "rent-it-here, leave-it-there" bike system was introduced. A dozen or more bikes are planted at stations around the city, and can be untethered with the help of a credit card and a smattering of French to handle the automatic system. You even get half-an-hour's worth of free pedalling before the €1-an-hour charges start. You wouldn't want to complete the Tour de France on one of these machines – correction, you wouldn't complete the Tour de France on one – but these slightly overweight bikes are just what you need to drift from one arrondissement to the next.
For the high point of Marseilles, though, you should hop aboard bus 60 (€1.70 for an hour's unlimited travel). It elevates you the necessary 154 metres above sea level to the Basilica of Notre Dame de la Garde – the brash, 19th-century topping for a city that celebrates diversity and defies uniformity. From the many viewpoints around the gaudy church, you see what Marseilles really looks like: a city that overslept and got up in a bit of a rush, yet whose soul outshines any scruffiness. Other religions besides Christianity are available, notably Islam. To take the North African pulse of Marseilles, go just one street south of La Canebière and you discover the Marché des Capucins – a souk by any other name, where all the good things of the Mediterranean are bought and sold; cacophony and colour come free.
After immersing yourself in commerce, settle back down to sea level. The Corniche that swerves south from Marseilles is an uncelebrated miracle of engineering; like the Great Ocean Road of Australia (featured on pages 4 and 5), it was a job-creation scheme – but was created a century earlier. From here, the scattering of offshore islands includes If, whose château was the prison for the Count of Monte Cristo in Alexandre Dumas' novel. The writer called Marseilles "the meeting place for the entire world". I call the city a film set for a dozen different movies.
The three miles of seashore drive is punctuated with deep inlets, into one of which has been deposited a perfect little Provençal fishing village, Vallon des Auffes. Like many components of Marseilles, it seems disconnected from the metropolis by everything except geography. And now the city is connected by just 360 minutes' worth of steel to London. The happy accident that is Marseilles is all yours.
Starting on Wednesday, trains from London St Pancras operated by Eurostar (08705 186 186; www.eurostar.com) will reach Lille in 1 hour 19 minutes and Paris in 2 hours 15 minutes. You can change at either station for Marseilles. Eurostar will sell you a return ticket to Marseilles, starting at £109 return, but not for the exact journey described here; the system does not allow so quick a connection in Paris. So to make the specified trip you should buy a return to Paris (from £59) and a separate onward ticket, eg via www.tgv.co.uk.
Simon Calder went nowhere near a high-speed train for his trip this week; he flew on Ryanair (0871 246 0000; www.ryanair. com) to "Toulon" (actually at Hyères ), then hitch-hiked to Toulon and caught a train (€10.20/£7) to Marseilles.
Sip a glass of rosé at Le Bar de la Marine, 15 quai de Rive Neuve (00 33 4 91 54 95 42); €2.50 (£1.80) including free nibbles.
Order bouillabaisse (€20/£14) at Restaurant la Plage, 47 rue de Suez (00 33 4 91 52 01 45). Closed Sunday evening and all day Monday; book ahead for Fri and Sat.