During the past few years, we train fans have formed the idea that railways might be on the point of a big comeback. The hope rests on the glories of our railway history, the environmental logic of rail and the unquestionable glamour of Eurostar, the first train for decades with the right arrogance about it. In November this year, all three will be celebrated, when St Pancras station — described in this erudite and readable book as a “wonder of the world” — becomes the terminus for the high-speed rail link to Europe.

St Pancras was built by the Midland Railway in the 1860s, when the ambition of our railways, if not yet their track mileage, was at its height. The station was constructed in two parts. Arriving passengers first saw the train shed, the railwayman’s term for a station roof. The one at St Pancras was the biggest yet built in Britain, and anyone waiting for a train underneath it while clutching a cardboard cup of railway coffee is still likely to feel strangely insignificant.

The shed was designed by William Henry Barlow, an engineer, and Simon Bradley’s description of how he achieved such “volumetric clarity” is illuminated by lyrical touches. The horizontal supports were buried underground, so that the station seems to be all arch, with no clutter of cross spars of the kind forming a “visual mist” at, say, Liverpool Lime Street. The design also minimised the contraction and expansion of the metal, so that there would be only a slight rise or fall of the crown, “like the shallow breathing of a mighty creature in its sleep”.

But St Pancras is better known for the Midland Grand, its disused gothic-revival hotel that dominates the Euston Road like a sort of levitating Dracula’s Castle, shamelessly upstaging its modest and utilitarian neighbour, King’s Cross. Its mouldering, cavernous interior could be inspected on guided tours until quite recently. Films were shot there, including — perfectly logically — Batman Begins, and the legend grew of a ghost, a man eternally walking up the beautiful, sinuous staircase.

The hotel was designed by George Gilbert Scott, whose character is vividly evoked by Bradley. He looked like Gladstone — huge brow and big features apparently chucked together by some creator in just as much a hurry as he himself would be for most of his life. Scott designed perhaps as many as 1,000 buildings. As Bradley notes, in England and Wales only Cardiganshire is “Scott-free”. He dashed about on trains, and was known for marching into half-built churches and ordering corrections, only for someone to gently point out that, in fact, the one he was designing was a little way down the road.

For all his hectic schedule, Scott spent thousands of hours in prayer, and for him gothic architecture was a style endorsed by God. It was a signifier of national identity, evoking the medieval origins of church and state, and of course any Johnny-come-lately railway company on the make (which about sums up the Midland) would want to borrow such gravitas. Bradley makes clear that Scott also saw gothic as a “go-anywhere style for the modern age”, and we are told how he accommodated it to the times (patterned glazing reserved for windows with less attractive views, steep roofs and gable ends not simply piled on but carefully employed to break the monotony of the London skyline).

To early-20th-century eyes, however, this attempt to marry the age of steam with the age of chivalry — not angels but engine drivers depicted on medieval-style capitals — was beginning to look rather peculiar, and by then the hotel was failing. Yes, the Midland Grand had a lift (or “rising room” as it was called) and a pioneering revolving door, but the great mid-Victorian hotels were all, in a sense, false starts, being attempts to accommodate hundreds using the technology of coaching inns. Bradley describes the dozen joints always roasting before the kitchen fire and the dust chute into which the ashes from the hundreds of fireplaces were poured.

The hotel paid a man 10 shillings a week to chalk up the scores in the billiards room; it incorporated 10 pianos and an Electrophone, “a one-way telephone . . . with an apparatus that allowed up to eight people to listen in to live concerts, public speeches and church services”. But by 1935, the hotel had been eclipsed by others featuring such mod cons as bathrooms, and it was turned into railway offices. In 1966, British Rail — hungry for rationalisation — nearly demolished St Pancras. It was saved largely because of a campaign orchestrated by John Betjeman, who, I would have thought, merits more than the two glancing references he receives here.

This is, though, a very small criticism of a work that Bradley, being both the descendant of railwaymen and the editor of the Pevsner Architectural Guides, might have been born to write. His book stands as one of the first of what will surely be many happy consequences of the St Pancras revival.