By Trevor Timpson
St Pancras station was built at a time of supreme confidence in British engineering.
The new canopy (right) echoes the pattern of the old roof (left)
The station was "a deliberate essay in saying we're going to be bigger and better than our rivals", in the words of Alastair Lansley.
The Midland Railway, coming to London in the 1860s, later than its rivals at Euston and Kings Cross, was anxious to impress.
The brick and stonework was near-perfect. The soaring roof was "detailed delicately" by Rowland Ordish, who had worked on the Crystal Palace. The station hotel fronts the main road with a wealth of gothic towers and pinnacles.
Mr Lansley is chief architect on the remodelling of the station - his 11th year on the project.
For him, the best thing about building a 21st century terminus from a 19th-century core is the sheer volume involved - a scale set by the great roof's height, added to by opening the building into the undercroft (basement) below.
"I've got to nip myself as an architect the whole time and say: 'Who would enable me to build this volume with nothing in it?'"
He speaks with pride of the immaculate brickwork on the reconstructed west side of the station as "21st century gothic". "Learn from the Victorians," he says, "and know your building inside out; then you can respect it much better."
But the new northern part of the terminus is not imitation Victorian. The homage is more subtle.
The canopy where the old and new parts of the station join has a ridge and furrow glazing pattern that echoes the original roof. As in the Victorian station, the supports of the new building form a regular grid, with the roof supports spaced twice the distance of the rail deck supports.
Where the old and new zones join, says Mr Lansley, "I think it's a delightful junction. Barlow had bricks; we have bricks, but they're glass bricks so we could make the extension as see-through as we could make it."
Engineer William Henry Barlow was the mastermind of the Victorian station.
The pillared undercroft once used for beer is now open to the light
"When we're touching Barlow we'll play God and pretend we're Barlow but when we pull away we can be as 21st-century as we can get it," says Mr Lansley. Still, there is a desire to be "subservient" to Barlow's station design, he insists.
Barlow raised the deck for the tracks five metres above street level, to enable the trains to cross the Regent's Canal to the north, and supported it on more than 800 cast iron pillars.
The huge undercroft that this created was for many years used for storing beer, transported by the Midland from Burton-on-Trent.
The world-beating roof, supported on 25 latticed iron arches 74 metres across, rose to a point 30 metres above the tracks.
There were practical reasons for the giant single span. A central line of pillars would have had to go down through the basement below, interfering with the storage area and making the ironwork much more complicated.
Light floods in
A wider span allowed for more tracks to store rolling stock, without internal pillars for trains to collide with.
But Mr Lansley feels there was more to it. "It was at a time when Britain, in engineering terms, was showing off with supreme confidence," he says.
The rebirth of St Pancras to accommodate Eurostar trains has preserved it and restored its former glories, but has also radically transformed it.
21st century gothic - the station's reconstructed west side
Barlow's roof, though wide and high, only reaches half way along the 400-metre Eurostars; so now the central concourse is at the north end of the Victorian station building, instead of at the south end of the tracks.
North of the concourse, the original Midland lines are on the west side, with platforms on the east for planned high speed services to Kent.
Passenger access is below the trains - through the very undercroft where the beer was.
The iron pillars still support the train deck - but a concrete deck above it has replaced the bracing which joists on top of the pillars gave to the arches on either side.
This has enabled spaces to be cut in the deck and light from the roof to flood the station as never before, and right down into the undercroft itself. The beer barrels long gone, this will house up-market shops. The trains are upstairs.
The Victorians were high-tech; so are we, says Alastair Lansley (inset)
The roof was reglazed according to Barlow's and Ordish's plans, with the ridge and furrow pattern of its glass restored - with the ironwork in its original sky blue.
"They were immensely high-tech," Mr Lansley says of the Victorians, "and we've been high-tech - so of course you're going to get a reasonable marriage out of it."
The newly-reopened station will house Eurostar, Midland Mainline and fast Kent trains above ground, with Thameslink below and close links to the Underground hub it shares with Kings Cross.
For Alastair Lansley, for many years a railway architect, there is a need to make sure that "not one of the train operating companies would appear to be the poor relation".
He says: "We raise the bar on everyone, and then you get a most magnificent international railway station."