high-speed trains will take the strain for thousands of Britons heading for holidays in Europe this summer, with packages in France and Italy in particular demand as the express rail network criss-crosses the continent.

With the opening of the first section of the Rhine-Rhone TGV enabling double-decker trains to race eastwards from Dijon to Besancon and Bellefort, and eventually to Mulhouse, France now has almost 1,200 miles of TGV track up and running.

Meanwhile, Britain remains mired in controversy about a second high-speed line possibly opening in 2026.

It has actually taken more than 30 years to piece together the current framework of high-speed lines across Europe, beginning when the so-called Rail Concorde linked Paris and Lyon in September 1981.

Germany joined in the early 1990s, then Spain (1992), which now has more miles of high-speed track than France.

Britain only joined the club with the opening of the second section of the Channel Tunnel, the St Pancras line, in November 2007.

Today, London-Cologne is only a four-and-a-half-hour journey via Brussels. London-Berlin takes just over nine hours.

But Giles Latham at train holidays specialist Treyn says the Dordogne region of south-west France and Tuscany are among his biggest sellers for spring/summer 2012.

“Travellers fearful of eurozone prices see a five-night train holiday in the Dordogne in the £500-600 bracket as great value, with four-course dinners and excursions,” he says.

Treyn and its sister company Great Rail Journeys say sales through travel agents are up by 80 per cent since last year and in 2012, more than 50,000 travellers will travel with the two companies.

Treyn has 93 journeys in its programme, 35 new for 2012.

Alex Roberts, marketing director at Great Rail Journeys and Treyn, says: “People want ways of going on holiday to Europe which don’t involve air travel. Incidents such as last year’s ash cloud boosted our sector by pushing people against air travel and onto trains.

“All our escorted rail tours to mainland Europe depart from St Pancras International, which sets a glamourous tone to the start of any holiday.”

At Ffestiniog Travel, Dan May says passengers leaving St Pancras around 8.30am reach both Barcelona and Milan before 10pm. And he confirms strong demand by rail buffs for Switzerland, despite its sky-high cost of living.

Four nights’ B&B in the lakeside town of Wilderswil, starting at £670, includes return Eurostar rail travel via Basle, and also two Swiss Saver Passes covering an unlimited number of journeys over four consecutive days on railways, boats and most alpine postbuses throughout Switzerland.

The offer applies to departures in April and May and September, October and November.

At French Travel Service (FTS), specialising in tailor-made rail tours and city breaks by Eurostar and TGV, managing director Bill Smallwood says: “Eurostar and the fast-growing TGV network are revolutionising the short-haul holiday market.

“They offer a civilised, more comfortable way of travelling, combined with an opportunity to see changing landscapes of France as you head south. One-week packages start at little over £500.

“When people say it only takes two hours to get to the Med by budget airline, they forget two-hour check-ins at the airport and lengthy transfers at the other end - plus hassles of security checks and delays at crowded airports.”

Eric Hutchins at Norwich-based Holidays By Rail says: “With 40 new rail holidays added for 2012, we see huge demand in America’s West Coast, and to National Parks in the US and Canada, with eight-night packages from around £1,500 plus international flights.

“Our customers see the rail journey as part of their holiday - while air travellers only begin their holiday when they have actually arrived.”

Rail operators urge travellers departing from St Pancras International to take Eurostar tickets to their local rail station when they book connecting journeys. They usually qualify for the cheapest APEX tickets for the journey into London.

INFORMATION: FTS 0844 8488843 and f-t-s.co.uk; Holidays By Rail 0800 0337960 and holidaysbyrail.com; Rail Europe 0844 8484070 and raileurope.co.uk; Ffestiniog Travel 01766 772030 and ffestiniog travel.com; Treyn 01904 734939 and treyn.co.uk.