Rail travel has never been more comfortable. The Western European network, and many Eastern railways, operate reliable, fairly well integrated services. You can take a good sleeper - in a perfect world they would all be operated by Deutsche Bahn's immensely comfortable City Night Line service - pretty much anywhere, to Madrid, Munich, Zagreb or Budapest.
"Air-conditioned trains now penetrate Eastern Europe,'' says Smith. "It's only when you get into the back of beyond - Moldova, Bulgaria - that you encounter Soviet-era models. In any case, I don't think children mind or notice. They're not fussy about what the trains are like.''
Several simple steps can make your life easier. "It's always worth trying to book seats around a table as you can spread out and the children can draw and play more comfortably,'' says Amanda Monroe, a spokeswoman for Rail Europe. "Some trains have specific family areas, with four seats around a small table. Two seats tip up to provide additional space for play or pushchairs; these spaces are available on some TGV services, Thalys services to Germany and the Netherlands, and other European services.''
Nor do you have to go overseas to experience a great family rail journey. Most UK train operators make some attempt at offering activity bags for children. This is a strong point for First Great Western, which can offer Paddington Bear-themed colouring pads and puzzles. We would arrive in Inverness on the Caledonian Sleeper and by lunchtime go Nessie-spotting around Loch Ness and stand just metres away from bottlenose dolphins at Chanonry Point.
Some of our most euphoric family rail moments have taken place very late, or very early, in the day, sometimes on the same day. When you arrive bleary eyed in a station at 6.30am, coffee and pastries never taste better. At night, once the children have finally raised the white flag and gone to sleep, one of you nips down to the buffet car. Looking out of the window as you pass through stations you've never heard of with a glass of wine at hand is pretty perfect for a travelling parent.
There are, though, two big problems: price and complexity. In five minutes you can book a flight on easyJet from London to Copenhagen later this month for as little as £75 return (NZ147.50). Rail fares from London to Copenhagen start at £194 return for adults and £105 for children in a six-berth couchette. To Madrid the fares are £205 return for adults and £185 return for children in a four-berth couchette. And to Berlin the cost is £159 return for adults and from £139 return for children in a six-berth couchette.
"People always think air travel is cheaper,'' says Mark Smith. "But you have to factor in the travel to and from the airport, and you can't travel without baggage on a family holiday, so you often get charged for that.'' If you happen to have a toddler aged two or three, they can travel free if they don't require their own seat and can sit on a parent's lap or share a berth on an overnight train. In Switzerland, Sweden, Denmark, Austria and Germany the age limit is six.
The key to the best price is to book early, though this can prove fiddly. Eurostar tickets go on sale 120 days ahead of travel, but most European trains can only be booked 90 days in advance. In Spain and Switzerland this drops to 60 days, making it hard, or risky, to secure the cheapest overall fare.
Finally, bring plenty of euro coins for left luggage, which can be time consuming to figure out, and pack light. Our biggest mistake has been to carry too many books and activities, most of which stay in the rucksack.
And don't forget antiseptic wipes: our three-year-old dedicated the time between connections to licking almost every telephone handle in Brussels Midi station. At least it should have helped him to build up immunity.
One thing above all is essential. "Whatever you do,'' says Smith, "make sure you pack more nappies than you'll ever need.''
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