Interview: Read all about it ... architect finishes Great British Disaster

Paul Vallely talks to Colin St John Wilson

He's endured more personal abuse than any architect this century, and has had no new commissions for a long time. But Colin St John Wilson, mastermind of the British Library, has no regrets. After all, wasn't Christopher Wren fired before St Paul's was finally finished?

There were two things I was worried about. First, I was late. But so was he. And it was eight years in his case, which made my 15-minute unpunctuality seem paltry. But the other thing was that my expertise in architecture is, well, shall we say limited, and I was there to talk to the man who has, for the past 30 years, engaged in the titanic struggle of creating the most expensive building ever constructed on these islands.

Colin St John Wilson is, in his own words, "the architect of the Great British Disaster". Otherwise known as the British Library, it is to open to readers at the end of this month - some 35 years after the project was first proposed, at a cost of almost five times the original pounds 116m budget and with room for around a mere third of the 3,500 readers and only half the 25 million books originally planned for.

On top of that it is the building that everyone loves to hate. Even before it was built, Prince Charles, in his "monstrous carbuncle" phase, likened it to "an academy for secret policemen". The art critic Jonathan Meades labelled it "a lump of bodging on a cosmic scale". And the House of Commons National Heritage committee compared the huge red-brick building to "a Babylonian ziggurat seen through a funfair distorting mirror" and damned it as "one of the ugliest buildings in the world". But it was not the architecture I wanted to discuss with him, so much as what it has been like to endure more than three decades of lack of co-operation, frustration and lacerating personal abuse at the hands of the great and the good.

"He's a kind of martyr," a friend had told me beforehand. "He had a vision and he's been broken by it." But the figure who greeted me in the foyer of the new building seemed not to match such a description. He wore a black corduroy suit with a vivid blue shirt and no tie. For a 75-year- old he seemed enormously sprightly and his speech patterns surprisingly modern. He waved his hand excitedly around the entrance hall with its floor of soft-coloured Purbeck stone, its columns of pitted travertine marble and its soaring white walls and curving ceiling. His critics, whose knowledge of the place is generally limited to its unprepossessing exterior, are, one suspects, in for a surprise.

"As an exercise in preconception and prejudice, there just isn't a parallel," said this Emeritus Professor of Architecture at Cambridge University, who was appointed to the project in 1962. He then immediately found some. Christopher Wren took as long to build St Paul's and was put on half-pay for 10 years and fired before the end. When the Houses of Parliament were built, Disraeli said that the architect should be hung in public. And the architect of the Sydney Opera House, Bjorn Utzon, still won't talk to the press after the savaging he received for his design.

"It's put me out of business," he says, simply. Since Prince Charles's remarks in 1988, he doesn't even get on the shortlists, let alone win commissions. "Being the architect of the Great British Disaster I have no work and my practice, the actual partnership, has now dissolved. The team of really fine architects - many of whom gave 12 or 15 years to the project - have dispersed." One of them was his wife Mary Jane Long. "She accepts no self-pity at all. If I whinge I'm told to belt up. When it became clear that we weren't going to get any more work she set up her own business and is doing well. I might now do some work with her. At 75 I haven't done so well that I can afford not to work now."

By the marble staircase to the new reading rooms he pauses to look up at the tapestry - the largest woven this century - which he commissioned of the painting If Not, Not by R B Kitaj. It is powerful, vivid and disturbing.

"That's the idea," he says. "Books should disturb." But should libraries? The reasons for the vitriol that has been poured upon him are manifold. But not least is the anguish surrounding the demise of the sublimely beautiful old reading room in the British Museum which was until recently the heart of the Library. A coalition of its present bookish users, former readers wistful for their romantic student days and traditionalists in love with the room's historic associations with Marx, Freud, Dickens, Wilde, Shaw and other lustrous names, together created a storm of fury which was fierce and unabated.

"It was very demoralising. But then most of my blood is stubborn Scots. My Dad also had a hard time [he was Bishop of Chelmsford and known then as the Bolshie Bishop]. He did a lot of hanging in there - opposing the government over the Spanish Civil War, making a speech in the House of Lords on the atom bomb, which was received in deadly silence. So I carried on." The unhappy thing is that it is not just his father who is not there to see his achievement. "Sadly all my family are dead," he says slowly, as if surprising himself with the thought, "and so are many of the friends I would have wanted to show it to."

The saga began in 1962 when it was decided to extend the British Museum's library in the heart of Bloomsbury. Wilson was then a lecturer in the school of architecture at Cambridge, and in private practice with the department's professor, Sir Leslie Martin. In 1964, the two were commissioned for the project, which one civil servant told them with masterful understatement "may take quite a time to build". Wilson, who had to his credit a number of university buildings, turned down the job as head of the architecture department at Yale to do the library.

Today he does not regret the decision, though it was to bring him 30 years of grief. "I've always really wanted to commit myself to something really big. Next to a cathedral, which is to my mind the most transcendent of buildings, a library comes next; it is in its way also a sacred building." But the first two schemes, on the museum's Bloomsbury site, came to naught. Then, in 1972, the Museum Library and the national Science Library were merged, by an act of parliament, to form the British Library. A bigger site was needed and one was found on the railway goods yard on the Euston Road to the west side of St Pancras Station where Wilson's library now stands.

When Shirley Williams approved the scheme for the last Labour government in 1978, the plan was a three-stage project. But a year later the Thatcher government began what was to prove a tortured process of cuts and changes. The first phase was subdivided into three phases. There then followed at least five major shifts in the planning. "It was stop-go for years. It was simply appalling. We never knew with each bit of funding whether we'd get the money for the next bit, and so it went on." During the waiting he kept busy working on the details, making more than 2,000 separate drawings and sketches for different parts of the library.

"We tried to be pro-active and keep working on how we would approach the next stage if it were approved. I had to keep staff on the payroll - you can't just chuck them out and then get them back in six months' time. It was so wasteful. We had to build things - like a secure reception area and a tunnel to deliver priceless manuscripts - which were going to be knocked down. It was a waste of more than pounds 1m. The government was pretending to be realistic but pulling up the plant every 18 months to inspect its roots and see how it's doing is the most expensive way to build."

Eventually the project drew the attention of the National Audit Office, the nation's spending watchdog. It launched an investigation which catalogued 230,000 construction defects. The Tory government had failed to provide adequate management of the 150 sub-contractors. For ideological reasons ministers insisted that the project should follow a "construction management" costing policy - instead of fixing the price at the outset, the government insisted on agreeing payments to contractors as it went along. The idea was to bring greater control and flexibility; the reality was a chaotic nightmare of sub-standard work. The newspapers had a field day with lurid, and not always accurate, reports about 200 miles of moving bookshelves which juddered, 5,000 sprinkler heads which were found to be rusty, and 2,000 miles of electrical wiring which had to be ripped up and replaced.

None of this was the architect's fault but he seemed to bear the public opprobrium. "One hard moment was switching on the car radio and hearing the tail-end of an interview with David Mellor, who was saying, 'The only thing wrong with the British Library is the architect.' It was libellous and completely cynical on his part; but he knew I wouldn't sue. Then there was William Waldegrave who began talking, when a lot of it was already built, of turning the place into a book store with a tunnel to the British Museum. That was the worst moment of all because going off at half-cock would have been worse than not doing it at all. It would have been deeply humiliating."

But Wilson enters on to all this reluctantly. He is most anxious now to let his building speak for itself. And so it does. The blank-walled exterior may look like an over-scaled version of a toy-town Tesco but it belies the grandeur of an interior which feels imposing without being intimidating.

The entrance hall is welcoming and self-explanatory. "You shouldn't have to ask your way in a public building." Up the broad stairway behind the reception desk is a central mezzanine which is simple to understand, to the left is the main Humanities Reading Room, to the right is the Science wing, at the back is the restaurant.

We mount the stairs, whose bannister rail is wound with a soft leather which entices the hand upwards. "I wanted to treat each reader with respect," he says, in the hope that each individual will savour the feel as he does. The doors are of American oak with handles of dark African teak. The rich smell of leather and wood mingles. "We sense spaces like bats. We hear them too. And smell them."

At the top of the stairway, the King's Library, a massive six-floor tower of black glass, shoots up from the basement to the high ceiling like a massive sculpture. "I work from inside out, and ask what is the task the feature has to perform. Then you discover the inherent poetry." The free- standing glass stack will display at its edge the 60,000 leather-clad, gold-tooled volumes of King George III's library in fulfilment of the royal bequest that the books should be on show to the public and kept 'entire and separate'. It is the source of a clever trompe l'oeil - the highly polished black marble surrounding the glass shelving gives the illusion that its sides plunge down into the bowels of the building where four separate levels contain 200 miles of shelves, all kept at a steady 17C and 50 per cent humidity.

We enter the main reading room. The curving line of its high ceiling is broken by levels of terraces which create the impression of hanging gardens. The result combines loftiness with intimacy. Where the old reading room provided a single environment, the varying heights of the new one create spaces in which readers of different temperaments can find a haven which suits them.

"The day it opens I will watch like a stoat from up there," Wilson says, pointing to the upper terrace, "to see how people choose the seats that will for many of them become a lifetime habit." Each leather-topped desk has a lamp, a plug for a laptop computer, a modem socket and a light to indicate that the reader's books have arrived along the conveyor belts of rolling wheels, which, on a daily basis, can deliver 25,000 books in minutes.

"I wish I'd brought my camera," Wilson says with sudden ferocity. He has been talking of how the room's lights increase in power as the daylight fades when a shaft of sunlight on the ceiling catches his eye. "Look at that light and the abstract patterns it is making." It's a flash of his vast enthusiasm; the key to the determination, patience and faith that have driven him.

"What keeps me going? A sense of history and a sense of purpose, which is partly classical, partly religious. I believe with the Greeks that it is in the nature of everything to fulfil itself. And I do believe with William Blake that everything that lives is holy and has a purpose. We are here to contribute, which doesn't mean you mustn't expect a fight."

Some fight. Wilson once described it as his Thirty Years War. Is it now won? "I will wait to hear from the readers. Then I'll know."

Deborah Ross is on holiday