For the frequent train traveller, a folding bike is the ultimate companion. You can take it anywhere: no booking, no peak restrictions. Just fold it up and put it into the luggage rack.

The Brompton is the weapon of choice for thousands of commuters. Its 16-inch wheels and ingenious hinges make it a smaller, faster fold than almost anything else. For the commuter who wants to take a folding bike on the train, Bromptons are unchallenged. They’re not cheap, but few bikes are better suited to train travel.

Many London commuter railways prefer you to fold your bike before you get onto the platform. (One, C2C, officially requires that it’s placed in a ‘protective carrying case’.)

But the 16-inch wheels are too small for touring or off-road adventures. If you use the train as an aid to touring, look for a bike with 20-inch wheels. These will provide a faster, more enjoyable ride on country lanes, while being just small enough to be carried on the train. Network Rail’s cycle guidelines say “fully folded cycles, with wheels up to a size of 20 inches in diameter, are carried without restriction on all trains”.

Strictly speaking, folding bikes are classed as luggage. The official rules (the Conditions of Carriage) say “not exceeding 30 x 70 x 90 cm in size”. This covers most 20in folding bikes, though you might need to take the front wheel off. We’d recommend getting a bike bag, such as the Tern/Dahon CarryOn Cover, to help convince sceptical guards that you’re just carrying luggage.

Folding bikes are available with 24-inch wheels, too. These can provide a near-road bike experience, but check the folded dimensions carefully before buying one for train travel. Be wary of cheap folders from Argos and friends, which are invariably a false economy.