Buy a second-class saver return ticket, on the day you travel if necessary, and you can transform a simple trip by train into a fully fledged, carbon-light, eco-worthy grand tour of Britain.
Little known even to regular train users, this ticket allows you to break your journey anywhere along the main line, as often and for as long as you like (within the validity of the ticket), at no extra cost. The only restriction, for reasons best known to the train companies, is that you can only break your journey on the return leg, not outbound. Here are three stop-over possibilities along three of Britain's longest railway lines.
Travel from Glasgow to London Euston with Virgin Trains and you can mix urban and rural pleasures. Stop at Carlisle, one of Britain's most historic towns with three top sights within a 10-minute stroll of the station: the Tullie House Museum; the massive 12th-century castle where Mary Queen of Scots was imprisoned; and England's smallest cathedral, famed for its medieval choir carvings, stained glass and blue ceiling covered with golden stars.
Take your second break at Oxenholme, gateway station for the Lake District. Hop on the spur line to Windermere, which also offers open double-decker buses to Bowness, where you can explore the lake by steamer, or Ambleside. Stop in Preston for a dramatic change of pace with Blackpool an easy 25-minute train link from the main north-west line.
Just 10 minutes into the ride from Penzance to Paddington, operated by First Great Western, you'll arrive at St Erth where a branch line will take you along the Hayle estuary to St Ives – hopefully bathed in that halo of Med-bright light that has drawn artists ever since Turner first set up his easel there in 1811. St Ives is home to the Tate which overlooks the surfers' beach of Porthmeor, and the sculptor Barbara Hepworth's studio is also close by.
Continue the Cornish theme with a break in Truro. Cornwall's only city has a pretty, part Georgian heart, a stock of interesting shops around the new Lemon Street market, and a graceful Gothic-revival cathedral – the first to be built in England since Salisbury after a gap of 600 years.
Totnes has one of the most historic high streets in Britain lined with 16th- and 17th-century buildings built by merchants during a golden age of cloth. You can walk across the meadows to medieval Dartington Hall, an arts and educational centre with a hotel, restaurant and shops.
And, depending on the tide, you can catch a boat to Dartmouth, following the snaking, thickly wooded valley of the Dart, then ferry across the river to Kingswear, where you board a steam train to Paignton followed by a number 12 bus into Torquay. With its knobbly geography, deep sea blues, terracotta cliffs and abundant greenery, Torquay – on a sunny day at least – could pass for the south of France.
First stop on the Edinburgh to King's Cross line, operated by National Express, is Berwick-upon-Tweed, south of the border. Nicknamed the Bath of northern England, Berwick's magnificent Georgian core – there are 260 listed buildings – is encased by an unbroken barricade of Elizabethan ramparts.
The track south to Newcastle hugs the Northumbrian coast, with stunning views for those who have bagged seats on the left. The city itself offers a rich seam of cultural attractions, as well as the Baltic Centre in neighbouring Gateshead, the biggest gallery of contemporary art outside London.
If you are travelling with the family go to Life, a colourful, noisy, hands-on museum giving serious science all the fun of a fairground. Then there's the model ship collection in the Discovery Museum, the Laing's collection of paintings with a high quota of pre-Raphaelites and terrific shopping in Grainger Town, the listed golden stone heart of Newcastle, which was conceived as a city of palaces.
And so to York where a short walk from the station will lead you into the heart of one of Europe's best-preserved medieval cities, dominated by the Minster, the largest Gothic cathedral north of the Alps. Other attractions include the National Railway Museum and Jorvik, where time capsules will carry you back to Viking times.
Virgin Trains (08457 222333; virgin.com/trains); Carlisle Tourist Information (01228 625600; historic-carlisle.org.uk);
Cumbria Tourism (01539 822222; golakes.co.uk); Blackpool Tourist Information (01253 478222; visitblackpool.com); First Great Western (08457 000125; firstgreatwestern.co.uk);
St Ives Hotel and Guesthouse Association (01736 796297; stives-cornwall.co.uk);
Truro Tourist Information (01872 274766; truro.gov.uk);
Totnes tourist information (01803 863168; totnesinformation.co.uk);
Torquay Tourist Information (0870 707 0010; englishriviera.co.uk);
National Express (08457 225225; nationalexpress.com);
Berwick-upon-Tweed (01289 330733; berwick-upon-tweed.gov.uk); Newcastle Tourist information (0191-243 8800; visitnewcastlegateshead.com);
York Tourist Information (01904 550099; visityork.org).