Simon Calder: Trains to Europe on track at last

The man who pays his way

All change: Marseille is to get a new train link

Spare seats are rare from British airports this summer, because UK airlines lead the world in filling planes. Charter carriers, the pioneers of low-cost aviation, aim to fly with every seat occupied. No-frills airlines, notably easyJet, use sophisticated "yield-management" – constantly tweaking prices – to fill nine out of 10 seats year-round. And to maximise the "load factor," airlines such as British Airways and Virgin Atlantic overbook: selling more tickets than there are seats. They usually predict correctly the number of no-shows, and get away with it.

Yet thousands of empty seats will depart from the UK this weekend for Europe. The spare capacity is on Eurostar trains from London to Paris and Brussels. High-spending business travellers demand a convenient schedule between the capitals, so Eurostar despatches a train every hour or two from early till late to Brussels, and more frequently to Paris. Each train has 750 seats, the equivalent of two Jumbo jets. And that implies plenty of empty seats in August as commercial and political life in the Belgian and French capitals slips into a deep slumber.

Handily for the train operator, hauling a seat from London to Paris or Brussels is cheaper by rail than by air. Eurostar can tolerate load factors that would prove disastrous for airlines. But this summer the company is responding shrewdly to the waste of space by selling £99 return fares for travel in August. You neither need to book weeks ahead nor choose anti-social departure times to get these tickets. For anyone within reasonable reach of London St Pancras, an impulsive day-trip for lunch in the Grand Place in Brussels or a picnic in the Place des Vosges in Paris is yours at the drop of a debit card.

If you can stay longer, the tranquil Ardennes and the Champagne region are within easy reach – though roaming free in a great European city when there's no-one home is a rare treat in itself.

The Sunshine Express

Another smart move from Eurostar: starting next May Day, a year-round rail link from the Thames to the Med.

At last. Currently you can catch a direct train to the French Mediterranean from almost anywhere in Europe (including principal stations from Moscow to Nice), except Britain. As work on the Channel Tunnel began, extravagant promises were made about through trains linking Scotland with Paris and Bristol with Brussels. The rolling stock for these "Regional Eurostar" services was built but never used for the intended purpose, and has now gone west: the carriages were sold at cut price to Canada, and were last seen rolling through Ontario. Likewise, trains from London deep into Europe were pledged, but in 20 years Eurostar has ventured little further than a ski train to the French Alps and summer Saturday services to Avignon and Aix-en-Provence (or at least the ungainly TGV station vaguely near the city of Cézanne). Now, a proper big city in an alluring location will appear on the destination board: Marseille. All the train traveller need do is sit and watch almost the entire length of France waft past in a speed-induced Impressionistic blur en route to la mer bleue.

The Sunshine Express, as I call it, will whisk you from a London mist to a Mediterranean heat haze – and from one great terminus, St Pancras, to another. Marseille St-Charles is an elegant, angular gare, courtesy of that towering engineering genius, Gustave Eiffel. From here, it is a 10-minute walk to the port along La Canebière, built as Louis XIV's avenue to the sun.

Marseille is an intriguing destination, in some places resembling a cousin to Algiers, in others a gastronomic heaven. Like other previous European Capitals of Culture, it is more rewarding after its year in the spotlight. The city's cultural infrastructure was transformed for last year's festivities and can now be enjoyed with less of a jostle.

You can also change in Marseille for a fast ferry to Corsica or a slow boat to North Africa, thanks to the network of trans-Mediterranean routes from the port. The new rail link could help shift the balance of travel away from aviation and back in favour of trains and ships. Flying to the city can be a dismal experience: Marseille-Provence airport has the most utilitarian no-frills terminal in France (against stiff competition from Lyon St-Exupery). And while the airport is convenient for Arles, it is an awkward 20 miles north-west of Marseille. City-centre-to-city-centre, the train could prove a match for the plane in time and money – and a benefit for the planet.

Bridging the gap

More good train news from Europe. The European Rail Timetable reveals a small piece of railway history has been forged amid the ripple of fortress-topped mountains and deep river valleys where Bohemia and Upper Saxony collide. An international link has reopened. Granted, it connects two towns that you may never have heard of: Dolni Poustevna in the Czech Republic and Sebnitz in Germany. They lie east of Dresden, where the international border throws a loop that temporarily places the Czech Republic north, rather than south, of Germany.

After the Second World War, both towns ended up on the Soviet side of the Iron Curtain, but the line between them was severed. New tracks have been laid and local trains now shuttle across the border. The main line between Dresden and Prague remains one of the most dramatic inter-city rail journeys on the Continent, but the reconnection will enable dedicated train travellers to take an even prettier route through the heart of Europe.