Light at the start of the tunnel

They used ploys, they used artifice, and it worked. The London Tube line to the Dome is an extravaganza of the age. Nonie Niesewand hears how architects conquered official meanness to build the stations of their dreams

"DON'T worry," Peter Mandelson reassured David Frost on his Sunday breakfast show as he discussed the Millennium Dome and its junior companion Baby Dome. "The Jubilee Line Extension will be up and running early next year." You bet it will. The Government's reputation hangs upon it, because it will be the main route to the Dome - New Labour's monument.

Mr Mandelson's reassurances were needed because construction of the tube route is running a year late, because of signalling problems. Apart from the convenience which the new line will bring to those working in London Docklands (including the staff of this newspaper) by giving them a rapid connection to the centre of London, it also provides London Underground with an opportunity to prove once more that it is a great patron of architecture, just as it was during the heyday of the Thirties.

Roland Paoletti, who is responsible for the station project, believes that London Underground needs to make its mark in the 21st century, "more like jazz than chamber music". So he chose a team of "rigorous structuralists" to endlessly improvise with their designs for 11 stations along the route. He believes that there should be no discordant notes, but no bland corporate uniformity either. Even a claustrophobic can handle the big wide open spaces he envisages with as much natural light beamed down.

Integrity is a word he uses a lot and he likes to remind people of his Tuscan roots and the unfinished Florentine churches that he loves. "If I can't afford it, I prefer to leave detailing unadorned, unfinished.There's a certain rigour to it."

Vigour, robustness, integrity are qualities he admires. Not stylistic flourishes. But drama, yes. Paoletti trained as an architect at Manchester with Norman Foster and worked in Venice with Carla Scarpa. Seven years ago he began the search for London based architects - they didn't have to be Londoners but they had to use the city infrastructure

The city will pour into Alsop's North Greenwich Station if the anticipated 12 million visitors to the Millennium Dome do arrive. Roland Paoletti doggedly fought to build a really big station here. But that was long before the dome - and all the traffic it would generate - was conceived. "You never ever put in an underground like a heart transplant after the development. Build the underground and let the city come to it."

One huge concourse in pale concrete makes it the biggest underground station in Europe. Jaunty blue-tiled columns take the eye upwards in this cavernous space to the silver bellied roof like a plane fuselage hovering high overhead. By comparison the tunnel for the trains are tiny. These changes in scale are as giddying as adventuring in Wonderland, and as reflective as a looking glass, which is curious because there is no source of natural light. The ticket office is a skewed steel framed window.

Paoletti's brief to the architectural practices who tendered for the job seven years ago was to make sure they let engineering inform their designs. "I remind architects when they get too pansy about detailing that this is a station, not a room. There's a railway running through it."

A latter-day Kublai Khan swopping Southwark for Xanadu, architect Richard MacCormac from MacCormac Jamieson Prichard built his Jubilee Line Extension station like a dome to beam light down 12 metres into caverns measureless to man. A half conical light well which sticks up above ground like a ship's funnel beams daylight down into the sparkling backlit blue glass mezzanine hall designed by Alex Tschenko. Once the computer configured just how 600 glass triangles could clad an elliptical cone, the architects invented a spidergrip-like system of fingers to hold the glass in a steel frame and allow subtle variations in the grip. A silk screened pattern changes from opaqueness at ground level to translucency at the top.

Known for their pure white polished plaster like travertine, MacCormac, Jamieson, Prichard cast it on site. Forty lorries drove around casting in one go the swooping drum-like entrance. Tapered steps exaggerate the Indiana Jones scale of this temple to travel. A big circular glass brick inspectors' booth is modelled on one designed in the Thirties by Hordern for London Underground. Richard MacCormac is funny about the time lapse his station went into, Tardis-like, from the original commission seven years ago. Then, the Tories saw art in public works as squandering of public money. So he introduced Alex Tschenko's brilliant glass wall as cladding, which it isn't. By the time Southwark planning committee worried over the half-moon lightwell jutting above ground, the architects had learnt to describe it as sculpture. The architects are most proud of the fact that by saving tunnelling on a 40-metre stretch they saved their fees four times over in the first six weeks.

The popular misconception that "design excellence doesn't come cheap" is unpopular with Paoletti. It grieves him. "Design excellence incorporates economy. Ugly little stations would have cost more. Take the integrity at Westminster between the Houses of Parliament and the Jubilee Line station by Michael Hopkins. It would have been very expensive to plan both buildings separately. His design cohesion makes it absolute."