As we all know, the percentage of schemes that make the leap from drawing board to postal address is pitifully small, but this does not prevent them from acting as catalysts in ways that are as unpredictable as they can be profound. The London Millennium Tower project was a case in point.
When the poet William Wordsworth gazed out at the City of London from Westminster Bridge on that celebrated September morning in 1802, he can have had no idea of the transformations its towers, domes, theatres and temples would be undergoing two centuries later. St Paul's Cathedral, for instance - in Wordsworth's day, nearly as much of an invader on the London skyline as Canary Wharf is considered to be today - had come to exercise an extraordinary power over development throughout the City. A complicated system of sight lines had been drawn up to protect glimpses of its dome, and thus control the height and bulk of any project in doing so.
If the remaining buildings still seemed asleep, as Wordsworth said, it was only because so many of them were unoccupied, like those in the maze of narrow streets around the Bank of England, where they were protected against demolition. At the dawn of the 1990s, what remained of Wordsworth's City - and that part of the City that was built after his death - was in thrall to the idea of preservation, as though Upon Westminster Bridge was going to seal its shape forever, while allowing its blood to leak away to fringe boroughs, the Isle of Dogs, or rival cities on the continent.
When release from this hypnosis finally came, it came suddenly. In April 1992 the largest terrorist bomb ever detonated in mainland Britain devastated one of the sleeping City's oldest financial institutions, the Baltic Mercantile and Shipping Exchange, located in St Mary Axe, a narrow street near the Bank of England. At first, the response to this outrage was to rebuild it, but time passed and a more realistic view of the cost of repairing it brought about another change. In 1994, the site was sold to a development company. Combined with two smaller adjoining sites, this sale created a prime 0.57ha freehold site in the centre of the City.
In this unpredictable way, the doors of opportunity opened for a new building.
The Baltic Exchange site had many advantages.
Miraculously, it was untouched by the invisible rays protecting St Paul's and it also lay outside the City's central conservation area - but, best of all, it was located in a cluster of older office towers whose construction had been permitted by an earlier regime in the 1960s. The tallest of these towers, then called the NatWest Tower, was a bare 200m high, but it was the tallest tower in the City nonetheless. Convinced of its potential, the company invited six prominent firms of architects to compete.
Every one of them proposed a tower. The winning design was also the most radical, a streamlined 95-storey, 385m steel-and-concrete-framed tower clad in glass by Foster and Partners. This building was designed to nestle within the cluster of existing towers and thus provide a coherent, rather than a fragmented, skyline. The London Millennium Tower, or LMT as it was christened, was a breathtakingly transparent structure, immensely innovative in its technical design and, with sky lobbies 30 floors apart, served by double-decker lifts.
It was also a structure that came straight to the point. It could have delivered a massive 160,000 m 2 of state-of-the-art office floorspace to the heart of the City, on the doorstep of the Bank of England.
But it was not to be. The LMT was never built, but without it there would have been no Swiss Re.