The craftsmanship of the carriages is breathtaking, even without much knowledge of what went into it. The wood interiors, with their inlays, veneers, marquetry and French polish, had to be made and fitted without lines or ridges. The exquisite sofas and cushions, the fold-out beds, the cleverly contrived bathrooms in the later carriages, are worth a long inspection.

Work on the exteriors is equally dazzling: woodwork, paintwork, brass decorations, coronets and variously contrived regalia combine for the regal whole. The word “carriage”, after all, has its origin in the horse-drawn era and initially the standards and comforts of that time were simply transposed to rail. “Railway carriage” was an exact description.

Visitors with an interest in engineering will find much to engage them: different gauges, the technical developments of various railway companies, how companies shared their technical discoveries, or did not.

After marvelling at the actual building of the train, the visitor can consider the lives of the royal travellers and how hard to imagine they are, as demonstrated by the peculiar arrangements made for their comfort. Queen Victoria, for example, is said to have been so afraid of an accident that the sight of a communication cord (the passenger’s emergency brake) distressed her. Therefore all the communication cords on her train were covered up.

Despite this anxiety and her own imposed speed limit of 40mph, the Queen loved her train so much that when the standard gauge was altered she wished to keep the same train. The carriages were ingeniously cut in half and fitted onto new undercarriage, so that the lower half conformed to the rails, the upper to her Majesty. Stretches of railway line were (and still are) given several days’ notice of the passage of a royal train. Nothing should impede it, in particular no one with inhospitable intent.

When Edward VII succeeded to the throne he called his mother’s train a “stuffy old tub” and ordered another. This one is now regarded as the ultimate in Royal train-building, with all the style of the luxurious journeys of railway legend. It lays heavy emphasis on dark green and has a smoking saloon where the King sat with two footmen, one to light and relight his cigar, the other to open and close the windows.

One enigmatic feature is the distance of seven carriages between the King’s sleeping carriage and that of the Queen; almost as far apart as the sleeping carriages for the male and female servants. Beside the King’s bed are six bell-pulls. They are marked: equerry, light, night, attendant, valet, and electric fire lighter (a person). None is marked “Queen”.

The Second World War brought an armour-plated royal train into service, its yellow and duck-egg blue interiors as austere as those of the Edwardian version were ornate. It has wireless transmitting and receiving apparatus so the King could stay in touch with the progress of the War and Mr Churchill could stay in touch with the progress of the King. This is an advance on Edward VII’s train which only had a Bakelite phone that was plugged in when the train stopped at a station.

Visitors to Palaces on Wheels have access to all the other wonders of the Railway Museum and may see the Royal Mail train as a loosely related artefact. It has a terrifying net for catching mailbags at points along the line, and a huge leather mailbag for throwing the sorted mail out again at stations.

Apparently both devices were prone to incontinence and letters could be scattered to the four winds as the train sped by. The post was sorted into pigeon holes within the carriage, a task that could be done while the train travelled at 60mph.

For schools, Palaces on Wheels has special relevance to key stage 2 Victorians, but the education staff will adapt all the museum’s material across the curriculum. History and technology are the most obvious areas but there is scope for geography, language and maths. Take the following statistics, for example - every time the Royal Train left the siding last year it cost Pounds 19,101. Well, on average. The train was used on 31 occasions during 1995 at a cost of Pounds 2 million.

For many of today’s younger generation, of whom up to 70 per cent are said never to have travelled on railways, train journeys must be the stuff of storybooks. Whether the royals can shunt Thomas into a siding, however, is yet to be seen.

Education office, National Railway Museum, York YO2 4XJ. Tel: 01904 621261