It’s been an awfully long time since British rail travel has been what you’d call alluring. Sleazy, filthy, cramped – maybe. But sophisticated, romantic, with a dash of Agatha Christie, a sparkle of Trevor Howard, finished off with an eccentric sprinkle of John Betjeman? Any relationship between the words “British trains” and “glamour” is long estranged.

But then there is St Pancras. I’d forgotten what it was like. As long as I’ve been alive the station’s famously phantasmagoric architecture has been veiled, cobwebbed, caked in soot and neglect. George Gilbert Scott’s gargantuan Midland Hotel out front has been derelict since I was in short trousers, haunting the Euston Road with its Gormenghast gloom and purposeless air. The hotel and the station werevictoriously snatched from British Rail’s demolition ball in the 1960s with the help of that great railway enthusiast Betjeman (unlike Euston down the road), but, for decades since, that victory has turned out to be a pyrrhic one.

William Barlow’s shed behind the hotel, the engineering feat of its day, had become so crepuscular that walking in catapulted you back to some distant time between the age of steam and the InterCity 125. It was romantic, in a way, but more Miss Havisham than Celia Johnson, its few trains trundling off to Kettering and Leicester rather anticlimactic within a stupendous building clearly meant as the start of journeys to destinations more exotic.

But look at Miss Havisham now. The station’s restoration, under the hawkeyed English Heritage and the architect Alistair Lansley (who worked on the Channel Tunnel rail link and is the last survivor of British Rail’s architects’ department), is breathtaking. Not exactly a babe, but restored, revived, with a new purpose to life. St Pancras has become the grande dame that her youth always promised. Come November 14, when St Pancras reopens (save for the Midland Hotel building, which reopens in 2008-09), it will have Paris and Brussels on its departures board. It will serve Luton and, in 2012, the Olympic Park too. But it is those new destinations, more exotic than the East Midlands or the Lea Valley, that has got its blood pumping again, mainlined through Britain’s only high-speed line, High Speed One, from Central London to the rest of the world. This is not just rebirth, it’s reincarnation.

Once you get past the humdrum of getting from A to B, travel is about the exotic, about possibility. Architecture is the same. Once you get past building a structure that stays up, it is architecture’s purpose to take you higher. Gilbert Scott and Barlow didn’t just build a mechanism for fast travel – revolutionary enough though that was in the 1860s – they built one whose very shape fast-tracked the imagination. The commuter, the ordinary Joe, had never been treated to such finery. King’s Cross next door, London Bridge across the Thames, old Euston or the new underground railway were pure Victorian utilitarian.

St Pancras, though, was romantic – Neo-Gothic, but from a time when Neo-Gothic wasn’t just nostalgic. Combined with high technology of iron and glass, it was weirdly (to our modern eyes) futuristic too, despite the fact that most Victorian architects at the time were still dithering over whether iron was respectable enough to be out in polite society, let alone combined with godly Gothic.

The combination created architecture of fervency, height, breadth and adrenalin. Think of John O’Connor’s 1884 painting From Pentonville Road Looking West: Evening, the fiery, polluted, Victorian sky pricked by St Pancras’s towering pinnacles. Has smog over a grimy neighbourhood ever looked more visionary?

No bones about it, Barlow and Gilbert Scott made St Pancras to be the greatest station in the land. No, not a station – a cathedral, its Gothic pointed shed, the widest single-span arch of its age, apeing lofty medieval Gothic naves, and piled high with allusive decoration to stoke the imagination, and gird the loins for the adrenalin rush of newly fast travel and the future.

Stripped of soot, all this is back with a mighty bang. It’s like digitally remastering a crackly 78, or retouching scratchy Victorians in colour. St Pancras is bright. The shed’s immense glass roof is dazzlingly clear, shedding light on to the platforms below. Its metal girders are painted what was found to be the original baby blue – demanded, no less, by its first stationmaster, who requested an artificial sky to replace nature’s original. The brick and stone of Gilbert Scott’s architectural casing is, again, almost orange bright.

The carvings are crisp: you will never see more wrestling dragons on a building. The details, right down to the mammoth Addams Family brackets and drainpipes out of a medieval torture chamber, are lavish. Whole new walls, arches and arcades, never intended by Barlow and Gilbert Scott, have been built but so dedicated has been the mimicry that you’d be hard-pressed to spot them. The building sings. And what a sweet note.

The added miracle, though, is the very cause of the original’s rebirth: St Pancras’s new life. There are five stations now housed in the building, where once there was one: the First Capital Connect line to Brighton and Bedford, deep underground; the Midland Mainline to Sheffield, and, from 2009, the North Kent line to Margate, both housed in the shed behind Barlow’s (feeble in comparison, but at least neat and simple); five Tube lines; and the new Eurostar terminal.

Lansley’s trick has been to keep such complexity simple. Each mini-station has its own quarter, sewn together by one main aisle – the Arcade – and two transepts. The Arcade runs north to south and is cut, with English Heritage’s blessing, like a canyon below the original station’s platform level, with vistas up to the roof, 37m (121ft) above. The transepts run east to west, one through the original building, the other, in use for a couple of years now, where it meets the new shed. The cross-section is as simple as the plan.

Barlow built his platforms on the first floor, leaving a huge crypt below for freighted goods to be stored. All trains, save for First Capital Connect and the Tube lines, still depart from up here beneath the glorious roof, while the crypt below has been freed up for the aisles, transepts and retail units – a forest of columns almost as mesmerising as the Mezquita’s in Córdoba. The new additions, in Fosteresque concrete steel and glass, oak parquet and slate, are good quality, but polite enough to sink into the background, as well they should when the foreground is as gaudy as St Pancras’s.

Just as in the 1860s, this is planned not just as a station, but a destination, the first piece in the regeneration jigsaw for a long-troubled and claustrophic neighbourhood. By making the building for the first time porous north to south and east to west at ground level, St Pancras is no longer a barrier, but integral to the street pattern. By making it attractive, with a farmers’ market, a gastropub (the Sir John Betjeman), independent stores and the much-heralded longest champagne bar in the world, hard against the trains under Barlow’s roof, it becomes a place in which to linger, not speed through. It becomes a civilised place, as it was in Barlow’s day, when station tea was served in porcelain, not polystyrene.

But all this is just bread and butter and revenue-earning possibility for the owners, London and Continental Railways. What really counts is the rush you get when Eurostar glides into the fantastical station, or when you ascend the travelator ramps with your suitcase from the crypt into Barlow’s cathedral.

Frankly, we, the Great British public, who have suffered for decades, deserve St Pancras. In one fell swoop British rail travel zooms from grim to glorious, to sophisticated, romantic. British rail is glamorous again, and just in the nick of time, too, as cheap flights start to lose their lustre. The French may have the TGV, the greatest train network in the world and warm buttery croissants waiting for you when you arrive. But we’ll always have St Pancras. And a pork pie and a pint in the Sir John Betjeman.

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