Jubilee

A hundred feet below Westminster, dozens of workmen are laying tracks along two new tube tunnels that stretch under the Thames, across to County Hall, and beyond to Canary Wharf and Greenwich. Close by, dozens more are busily transforming an extraordinary cavern into the new Westminster station. These subterranean activities are part of the Jubilee Line Extension Project, which, after years of being stigmatised as the curse of the capital's transport system, is fast becoming a very promising reality.

On a sweeping route across south and east London that takes in Bermondsey, Docklands, Greenwich and Stratford, the extension includes the development of existing stations such as London Bridge and Waterloo. New stations, like the delightful building at Bermondsey, are virtually complete. Others are taking shape, including Sir Norman Foster's stunning addition to Canary Wharf, and what is thought to be Europe's largest underground station at North Greenwich, designed by Alsop & Stormer. A fleet of 59 new trains has been ordered, with some already in use on the existing Jubilee Line. And at Stratford, the state-of-the-art depot is ready and waiting for an opening day in September 1998 .

This is Europe's largest current construction project, an engineering enterprise of phenomenal scale and ambition. In 16 months, it will provide the capital with the transport equivalent of a new lung, breathing life into the slumbering giant of Canary Wharf, clasping south-east London to the bosom of the West End, and creating development opportunities throughout the city, not least the hitherto deprived areas of Southwark and Bermondsey. Where transport leads, cash will follow.

Accompanied by my guide, Bill Jobling, the JLE's senior inspector on this stretch, I entered the new system via the disconcertingly sleepy gateway of St James's Park. Kitted out with a hard hat, I was taken to an access shaft in the park, put into a cage and shot down 100 feet. I stared, in the general direction of the Thames, into an eerily lit, smooth-walled tunnel. The schoolchildren and summer tourists, clogging the streets I'd left behind, would hardly comprehend the huge spaces being carved out beneath them.

The tunnel itself was effectively finished, and merely waited for another team to come and lay the track. We walked along the escape walkway, beside the track bed, under the Thames. As we approached Waterloo, there was a flurry of activity: men and machines were still making this section, and there was a hubbub of noise and dust and splashing in puddles. "Ants working underground," commented Jobling. Then we continued up a ramp, where soon there will be escalators, carrying passengers to their exit at Jubilee Gardens

As we emerged, Jobling talked about the fraternity of tunnellers. He said that many of them had also worked on the Channel Tunnel and on other schemes all over the world: "There's one family - fathers, sons, uncles, cousins - who travel all over and take their wives with them." They had given their tunnelling machines fond nicknames: Sharon and Tracey, St James the Mole, the Bermondsey Burrower, and the Giant Muncher.

Over 22,000 jobs have been created extending the Jubilee Line. Statistically, the whole project - the creation of 11 stations and two tunnels of more than 12 km each, plus all related works - will have taken just five years to complete by its deadline: set that figure against the 20-odd years it's taken to build the still unopened British Library. The 118 new escalators for the stations equal the number across the rest of the whole tube network, while 34 lifts make it the most sympathetic tube system in the world to disabled people. At 38 metres down, the new Westminster Station will be the deepest construction in London; while the Canary Wharf Tower, Britain's tallest, 50-storey building, could be laid down in the station with room to spare.

The JLE has also revolutionised tunnelling in Britain. The gravels and sands of south London have deterred tunnelling in the past. Contractors are now able to dig using a new tunnelling machine which applies pressure to the ground it's excavating and keeps the ground-water at bay. Less successful was the use of a controversial system, the New Austrian Tunnelling Method, for dealing with unusual tunnel shapes; it involves the spraying first of concrete over exposed earth, and laying down a more permanent lining later (the conventional method does the job in one go). An accident in a Heathrow Express tunnel led to the NATM being banned for several months.

The idea for a tube line linking the West End to east London had been mooted since the 1940s, but was not seriously pursued until the early 1990s, when the Thatcher government capitalised on an offer by the original developers of Canary Wharf, Olympia & York, to help fund such a route on condition that it passed through Docklands. Eventually, after the little difficulty of O&Y's receivership, its pounds 400 million contribution was assured by the company which succeeded it, Canary Wharf Limited, and the project approved. Aside from one other private contribution, from British Gas, the Government has paid the remainder,

Just as crucial as the private involvement was London Underground's decision to invite the architect Roland Paoletti to become architect-in-chief. An Italian, born and educated in Britain, Paoletti's influence on the project has been crucial. He was determined, above all, to give the project an unstoppable momentum before the Government could change its mind, but he also selected some of the country's most innovative architects (including Michael Hopkins, Chris Wilkinson and Will Alsop) to design the stations, and, importantly, broke with the tradition of design conformity within LU stations that was established with Charles Holden's classic stations of the 1930s.

"The London Underground is a sacred ruin, a terrible mess but with a great history," says Paoletti; he is a man of incredible passion, who rushes around the station sites with indefatigable energy, despite his slight lameness and ever-present crutch "I didn't want to go against it. But, at the same time, London in the Twenties and Thirties was the transport hub of the Empire: that's why the stations were similar, that's why everything was painted red! It was a world of corporate identity - that was the spirit of the age. But I really don't believe that is the spirit of the age in the London of the Nineties."

Paoletti's masterstroke was to give his architects free rein while insisting on a generous sense of space with, where possible, natural light, and coherent routing through the stations. He says he was influenced by the character of the East Enders whom the JLE will principally serve. "These people have always been an independent, wild bunch, and I thought: why not give them something a bit better than the rest of London - something new, more optimistic." The stations vary enormously but have common characteristics. Foster's scheme is 300 metres long, with entrances via elaborate glass domes in the roof of the building, and a dazzling procession of 20 escalators. Canada Water, by the JLE team, features a giant glazed drum entrance through which light pours into the building, right down to the platforms, so the station has a cathedral-like presence. Ian Ritchie's design for Bermondsey is Paoletti's own favourite; he sees it as a masterful variant on the traditional, corner-site LU station. Safety is also a key feature: all stations have platform-edge safety screens, which only part when a train has arrived and opened its own doors.

"The Jubilee Line will now be the most interesting line on the underground because every station is different," says Paul Finch, editor of The Architects' Journal. "They've got some of the best designers in the country working on this stuff." But there are those who believe that the JLE is an albatross around London Underground's neck, a luxury whose cost would be better spent on improving existing lines - such as the Northern - which are in appalling states of disrepair and inefficiency. This argument became more vociferous at the end of last year after LU bosses reported a delay of six months and an enormous jump in the JLE's budget by pounds 700 million to pounds 2.6 billion, with the then Tory government insisting that LU pay the deficit out of its annual budgets.

Finch is having none of the criticisms. "This is the most significant addition to the Underground since the Victoria Line," he repeats. "I think it's a triumph against all the odds - political crises, the questions over methods of tunnelling, some pretty fierce opposition. It's an heroic civil engineering achievement."

If Labour takes the same view, which it should, then it may well confirm the speculation that it is going to bale out London Underground with a one-off payment. What's more, a positive view of the achievements of the Jubilee Line ought to deter any thoughts that Labour might harbour of pursuing the Tories' plan to privatise the tube system. The JLE has developed, albeit with some problems, a public sector project aided by an injection of private sector cash. Such partnerships might give the rest of London's beleaguered tube system the urgent help it needs.