They've gone all en-suite at the 'cluster of towers and pinnacles'

The old St Pancras railway hotel is about to reopen. It's a sensitive restoration with modern comforts

Size matters. A few weeks ago the first of numerous Olympic rings that will grace London's landmarks appeared on the concourse of St Pancras International railway station. Seventy feet across, 30 feet high, the rings have (hurrah!) succeeded in shifting the limelight away from the hideous oversize bronze statue of the lovers that used to dominate the platforms.

And that has to be a good thing. Despite being 30 feet high, the lumpy couple only serve to diminish this great gateway to London. They are a salutary reminder that big is not automatically beautiful.

The captains of industry who commissioned the Midland Grand Hotel at the new railway station in 1866 could easily have made the same mistake. They wanted a monument for their times, one that reflected the prestige and power of the railways (the internet boom of its era) – they sought a building that would rank with the landmarks of Europe. The architect they chose, Sir George Gilbert Scott, supersized them. He gave them a castle and a cathedral rolled into one.

It is easy to forget that the Gothic Revival style of the whole caboodle fell out of favour for many years, with serious moves by British Rail to demolish it in the 1960s. Sir John Summerson, the architectural historian, famously described St Pancras as "nauseating and unworthy of special protection". Luckily, the building also had its fans, including poet laureate John Betjeman, who fought for the "cluster of towers and pinnacles" to win Grade I listed status in 1967. Betjeman's role in the salvation of St Pancras is commemorated at the station by another statue (mercifully on a more human scale than the lovers).

The latest saviour to line up behind Betjeman is developer Harry Handelsman, whose Manhattan Loft Corporation is resurrecting the Midland Grand and relaunching it as the five-star St Pancras Renaissance Hotel. Handelsman is an unlikely champion of the British Imperial project. Speaking in a clipped mid-European accent, he enthuses: "London is an amazing city, which has new things happening on an almost daily basis, but what happens here for the first time is you get introduced to Imperial Britain."

The mood of the times has changed. Such is the reverence that Gilbert Scott's pile commands these days that the new 120,000 square foot extension called Barlow House (running along the west side of the station on Midland Road) has been designed in pastiche style to fit in, and enjoys instant Grade I listed status simply by association with its parent.

All eyes, however, are on what has been done to the old block, known magisterially as the Chambers. There was no chance that the Midland Grand could ever return in exactly the same configuration as it was when it last served as a hotel in 1935. Gilbert Scott's hotel may have been the height of luxury when it opened in the late 19th century – only the Langham Hotel in Portland Place was (marginally) more expensive to stay at – but it dated rapidly. The vast building was not only exorbitant to heat and maintain but it was also not future-proofed in one critical way; the 300-room hotel had just five bathrooms. Inevitably, when the en-suite bathroom became a standard requirement for discerning 20th-century travellers, the hotel was doomed.

The 38 suites of the Chambers building are now all equipped with bathrooms, but due to the building restrictions imposed by the listed status they had to be installed within the rooms – in effect, rooms within rooms. The ceiling headroom gradually lessens the higher up the building you go; so the grandest suites are on the first floor, where the 18ft clearance is almost intimidating. These rooms were built for giants, or more likely for people whose self-image tended towards the gigantic.

The Midland was a hotel for important people on important business in the capital of an important country – at the height of its imperial power. Some of that sense of being at the hub of the world is retained by the frenetic activity that surrounds you. St Pancras International serves a million passengers a week. Travellers constantly boarding and alighting the Eurostar fleet can be seen from the windows of the rooms that face the concourse, while rooms on the other side of the corridor look on to the six-lane cross-town traffic of Euston Road. The rumble of six Tube lines also resonates upwards from the subterranean coil of tunnels. This was never a quiet hotel, but for anyone who thrills to the thumping pulse of big cities it is an exciting one.

The 189 rooms in the modern Barlow extension do not have the grandiose proportions of the Chambers and cannot hope to reproduce the experience of the Victorian hotel. The new rooms are, Handelsman admits with refreshing candour, "simply to make the hotel viable because otherwise we would only have had about 40 suites".

Guests staying in either wing benefit from the showpiece public areas. One such is the Ladies' Smoking Room, dating from 1898. It was, in fact, for the use of all smokers, but got its name by being the first room in Europe where women could join men in smoking publicly. The granite pillars, carved masonry and fireplaces have been buffed back to their former glory. They are, however, upstaged by the sumptuous ceiling – William Morris-style foliage, Gothic geometry, and gilt highlights on a delicate duck-egg blue base. This is a meticulous re-creation of the original ceiling which was, unbelievably, plastered over at some point.

Equally impressive is the care lavished on the famous grand staircase that sweeps up to the top floor with the swagger of a medieval potentate. The feature has long been visual shorthand for art directors seeking to evoke the Gothic, and has featured in many movies, including two of the Batman franchise. Ignominiously, it was also forced to earn a crust during the lean years of near dereliction as the set for the video of the first Spice Girls single, "Wannabe".

This latest revival of the Gothic Revival has not come cheap. The wallpaper in the sitting room of one suite alone was re-created at the eye-watering cost of £47,000. It is easy to see where the £200m investment has gone.

While the restored splendours of the original Midland have the capacity to wow, you are occasionally left with the nagging feeling that the sheer audacity of Gilbert Scott's original vision has been subjected to committee. Much of the hotel has an overlay of repro art deco furniture and furnishings thrust on it, which is a safety first choice but doesn't really bring much to the party. Neither does some of the artwork – by an eclectic bunch of modern artists including Joseph Beuys, Bridget Riley and Richard Prince (much of it from Handelsman's cherished private collection) – always feel like an obvious fit.

The "restoration" takes wings when the modern designers have been liberated from a surfeit of reverence and allowed to engage with their Victorian predecessor. The Marcus Wareing restaurant, set to open in the crescent section of the building, is a case in point. The graceful curving room suffered severe corporate vandalism during British Rail's tenure of the hotel. The lace-like cornicing was hacked through to secure the fixings for a suspended ceiling and the green Connemara and red Devonshire limestone columns of the room were caked in layers of blue paint. The room has not simply been returned to its original state but been propelled with the addition of modern chandeliers, mirrors and paintings into the 21st century.

The original entrance hall to the hotel next door is being repurposed as a bar, and is even more exciting. The archive photos show a utilitarian hallway that guests would have processed through. In its new incarnation the room is a riot of ornamentation – the stonework is picked out in gold leaf, the newly stencilled ceiling is profuse with colour and detail – but best of all are the huge brass bell-shaped lamps that descend in a spiral from the jewel-like ceiling rose. It is a fantastical blending of old and modern – which is what Gothic Revival was all about the first time around. The new Gilbert Scott bar will be serving cocktails shortly, but the room is intoxicating enough without a drink.

"A train station as a rule," says Handelsman, "is the sort of place you arrive at and want to leave as quickly as possible. It wasn't always like that."

And after the decades of neglect St Pancras isn't like that – again. Big, bold, loud and proud the station has recovered its mojo. Now, will someone please cart that statue off to a suburban park where the pigeons are waiting.

The St Pancras Renaissance (020-7841 3540; stpancrasrenaissance.co.uk) officially opens on 5 May. Double rooms cost from £360 per night.