There is, of course, no great virtue in building so high, and it has been done many times before. Structural engineers believe that we could, if we wanted, build "The Illinois", Frank Lloyd Wright's dream city-in- the-sky that would have punched its way 5,280ft, or nearly one whole mile, into the Chicago sky. Wright drew up fairly detailed plans for this architectural behemoth 50 years ago. The tallest building in the United States is Sears Tower, a dark and brutal structure, 110 storeys and a mere 1,454ft high, although topped with twin television aerials that stretch it to a vertigo- inducing 1,707ft.
Some years ago, I rode an elevator to the top of Sears Tower to watch the sun setting over the boundless wheat plains that stretch west from the Windy City. At least three generations of a Vietnamese family, new to the country, came to the top with me. They screamed all the way to the observation gallery, which was a little unnerving, and it took massive powers of diplomacy for the Tower's security staff to usher them back on to the last elevator down. Quite simply, they were petrified, and absolutely aghast that other peoples' children had been allowed to press their noses against the glass with a 1,454ft drop beneath them.
This episode proved two things: one that very tall buildings are somehow unnatural, and second, that, even so, there is nothing especially difficult in erecting them and making them safe. The Empire State Building, at 1,250ft the world's tallest building for decades, has never been a cause for concern even though it was built at breakneck speed and, famously, was crashed into by a low-flying B-25 bomber during the Second World War.
Given that we know we can build up to a mile or even more, why all the bother to reach ever higher into the sky, especially in cities like London that have rarely pushed their roofscape above 300ft?
If we really want to build in the sky, surely we would be better off paying our best architects and engineers to contribute to the design of orbital space stations which have the virtue of promising new insights into both life on earth (its origins and its sustainability) and life elsewhere, of pushing design into altogether new directions?
Looking through the 1996 Guinness Book of Records, with its lists of tallest structures - (2,063ft: the Channel 11 TV transmitting tower between Fargo and Blanchard, North Dakota), tallest tower (1,815ft, CN Tower, Toronto), tallest chimney (1,377ft, Ekibastuz power station, Kazakstan), tallest obelisk (555ft, Washington Monument, Washington DC), tallest flagpole (525ft, Panmunjon, North Korea) and tallest house of cards (16ft, or 83 storeys, by Bryan Berg of Spirit Lake, Iowa, 1995) - one sees that tall structures fall into two simple categories: those like TV masts and power station chimneys that are tall for purely functional reasons, and those like flagpoles and buildings that are designed to get one over their rivals. North Korea's 525ft flagpole, for instance, stands on the border with South Korea; its exists merely to intimidate.
In a similar fashion, country's and cities still compete with one another to build the biggest or tallest building to prove that they have the world's or nation's most muscular and fastest rising economy. This was certainly true of the United States from the 1890s, when Manhattan's skyline, for example, became a outward sign of the world's most upwardly mobile economy, and the first 1,000ft buildings appeared. In recent years, architectural commentators have linked economic performance with building height, noting that the world's tallest buildings are now to be found in the "tiger" economies of South-east Asia, such as the new Petrona Building in the Malaysian capital, Kuala Lumpur. Now the highest building in the world at 1,483ft, it was erected specifically because the country's long-standing prime minister, Mahathir Mohamad, wanted to make a statement to the world about the economic progress his country has made.
Which is more or less true, but does not explain the fact that Britain is still in the skyscraper race in 1996, when our economy is performing moderately well but could hardly be called dynamic. Perhaps a new generation of tall towers in Britain is a signal to South-east Asian investors in this country that we are still capable of dynamic action and are not utterly passive as we wait for others to run our economy for us.
In fact, the reason for building so high is nothing like as complex as this. No offence to Norman Foster, but wanting to build higher and higher in Europe at this late stage in the skyscraper race is a bit like the pissing games boys play in primary school urinals; who can wee the highest. As boys grow up (try to, anyway) they want to shin up the highest ropes and climb the highest walls while dreaming of joining the likes of Chuck Yeager, the great American test pilot, in the competition to fly the highest - and ultimately, if only they could, to shoot into space.
In other words, wanting to reach for the sky is a natural enough urge, although tall buildings themselves are intimidating and unnatural to those who, for all sorts of reasons - vertigo, fear of lifts, seen Towering Inferno one too many times, worry about the way tall buildings lean with the wind - prefer to keep their feet planted firmly on the ground.
It can be argued that the skyscraper is a bad neighbour to surrounding buildings in historic city centres where, until the invention of the lift towards the end of the 19th century, few buildings were ever more than eight storeys high, not because it was impossible but because only a masochist would have wanted to climb any higher up stairs. To an extent skyscrapers are selfish buildings: designed to be vertical cities, or at least a representation of the city (complete with offices, shops, cafes, gyms, flats and their own transport system, the lift), they offer a world remote from city life as experienced at street level. They are monumental, essentially isolated and a world unto themselves.
In this sense they are, although this might seem an odd thing to say, closely related to Greek temples: the Manhattan skyline is a latter-day Acropolis. Why? Because, Greek temples were designed to be a world unto themselves. Each was an ideal building and was meant to be experienced as a particular, specific and individual experience. Despite fascinating and even eccentric attempts by Beaux-Arts architects and theorists in the late 19th century to prove that the temples crowning the Acropolis were somehow laid out according to the laws of some sacred or otherwise deeply significant geometry, the case remains unproven. It can be argued that the lay-out of the Acropolis is as haphazard or as pragmatic as that of the serpentine street plan (if you can call it a plan) of the City of London from which Foster's 1,200ft tower may yet rise above the Barbican and St Paul's Cathedral.
In other words, a pragmatic grouping of brilliant yet selfish buildings may have a beauty denied even the most lovingly planned city centres. This certainly seems true of Manhattan, where the forces of private enterprise gave us one of the most memorable and inspiring of all city skylines. However, it is not as simple as that, for the city fathers endowed Manhattan with a rigid street plan - the gridiron - which ever since has ensured that out of entrepreneurial chutzpah came civic order: Manhattan was ideally ordered to meet the rise and rise of the skyscraper.
In cities like London and Paris, however, the siting, the desirability, of 1,000ft plus buildings, is part of a different equation from that producing central Manhattan. A densely-packed city centre with an essentially low skyline can only give in to a few skyscrapers if it is not to be swamped, and light and views from existing buildings are not to be stolen away by lofty intruders.
A way to design a skyscraper that we can all admire for the centre of European cities is to make it as ethereal as possible, by way of contrast to the stocky buildings it rises above and to reduce its bulk as far as possible. In his design for the as yet unbuilt "Tour sans finis" of a few years ago, Jean Nouvel proposed a skyscraper for Paris that, unlike the clumping Tour Montparnasse, got lighter and more transparent as it soared ever higher; at certain times of day, its peak would have appeared to have vanished altogether.
So, yes, as long as it was light and ethereal, London could cope and even benefit from another selfish skyscraper. But, unless it is very special and offers a real advance on a building type that muscled its way on to the architectural scene a century ago, we should be very wary of the attraction of height for height's sake.