“Interrail is now embedded into the travel culture of some families.” So says Susanne Kries, co-author – with Nicky Gardner – of Europe by Rail . I had asked the authors for their thoughts on what I believe is by far the best winter discount in the travel realm.

Here’s the deal: buy an Interrail pass by 17 December , and you get a straight 25 per cent off. You then have 11 months to start using the thing. This ticket enables you to catch unlimited trains in many northern European countries: Germany , Switzerland, the Netherlands, Belgium, Austria, Scandinavia and almost all of eastern Europe.

With some care, you can also travel for no additional cost in France , Spain and Italy – though many express trains require a reservation and a further payment. Hop aboard a French intercity train without paying a supplement, and the ticket collector may barely conceal their glee when fining you €35/£29 for the transgression. Accordingly, I recommend using an Interrail pass only in one of the no-surcharge nations.

But the new promotion represents excellent value for those who want a low-cost, high-reward travel itinerary for next summer. With a one-quarter saving, the cheapest “Global Pass” (allowing travel in 33 countries) for an adult between 28 and 59 costs €213 (£178). This buys any four days of travel within one month.

You might conclude that almost £45 per day is not the travel bargain of the century. Yet, if you use Interrail wisely, it can be. On a journey .