There are so many building projects in the City of London, the financial district of the capital, that looking up at the cranes is enough to make a visitor dizzy.

The wrapping is soon coming off the Walkie Talkie skyscraper, and a number of other towers with names like the Helter Skelter are slowly but surely getting off the ground.

There is no other place in the country where the creative-destructive spirit of capitalism takes on a more concrete form than in the City. With just 8,000 residents, there is almost nothing stopping developers from knocking buildings down and starting from scratch, making more space for the financial firms and fast-growing technology companies that populate this corporate oasis. The streets of London may be paved with gold, but it's usually hidden under a layer of builders' dust.

The towers that were thrust into the City skyline in the financial Big Bang of the 1980s are now facing an unusual problem. The NatWest tower, finished in 1981 and once the country's tallest building, has been around for so long that it has passed from being a modern monument to banking largesse into something of a national treasure.

Buildings more than 30 years old become eligible for listed status, and English Heritage has sent round its inspectors to the NatWest tower, as well as about a dozen other City sites, in the hope of getting the Government to protect them as landmarks.

The owner of the NatWest Tower, which is now known as Tower 42, is South African billionaire Nathan Kirsh. Word on the City's gilded streets is that his firm and others whose buildings are involved are awaiting English Heritage's proposals with apprehension.

Elsewhere in the country, this protection might be seen as a plaudit instead of a pain, but companies here don't tend to keep their buildings long - and some of the 1980s blocks are already earmarked for demolition.

"Developers are thinking about whether they attract listings 30 years down the line," says the City's planning chief Annie Hampson. Architects in the City have to balance their designs between making the new banking bases distinctive, and doing such a good job that the owner is slapped with a listed status come 2040, making the building more difficult to sell or change. "What I think the City is very concerned about is that we don't end up with too much post-war listing," added Ms Hampson.

Meanwhile, the City's planning office is trying to ensure the dash to build also brings something of value for the people who actually use the towers.

The new roof garden at the top of the 160-metre tall Walkie Talkie, for example, will be free for visitors at the insistence of the City of London.

"Historically it's been a bit of a financial closed shop. We are very keen to be seen to be engaging with the rest of London. The dichotomy of old and new buildings is what makes it attractive," said Ms Hampson.

But the City won't be allowing more residences within its walls, despite a housing shortage in London.

Between the building work and the bars filled with bankers, it's still considered an unsuitable place to live.