Out of all of Britain's cities, there's one that stands alone.
London.
Looking down in the capital today, what's obvious is the sheer scale
and complexity of this sprawling metropolis.
But how London came to look the way it does
can also be seen from above.
Because, 60 years ago,
the Royal Air Force photographed the whole of London from end to end,
and left us a unique record of a city torn apart by war.
Now exactly the same process is being repeated,
matching the original survey shot for shot.
And by directly comparing London then with London now,
we can tell the story of the greatest transformation
in the city's history.
It's a transformation that continues
faster now than at any time since the war.
This is the future face of London,
a future that's being designed and built already.
London's transformation began on September 7th, 1940.
300 German bombers flew in from the east, following the line of the river.
They arrived here at 6.45 in the evening, and looked down on their target,
the heart of London's docks.
It was the end of a beautiful summer's afternoon
and London was about to change forever.
We know exactly what happened, thanks to a series of photographs
taken by the German planes as they dropped the first bombs on London,
on day one of the Blitz.
What you see in this sequence of pictures, which runs
from Woolwich more or less to just east of the Isle of Dogs,
are a formation of bombers. Then you see the bomb load
being dropped by the aircraft which is carrying the camera.
You can see also the impacts trailing across from the other aircraft,
falling short in the river - you can see the splashes there - and the flashes
of impact in the steelwork of the gasworks, which, of course,
is THE major supplier of gas to London at that time.
Subsequently, you see the impacts of the bombs hitting the river,
and you can see the fires beginning in the docks,
which were part of the great conflagration of 7th September.
What you're looking at here is probably
the most devastating change to London since the fire of London in 1666.
You're looking at, effectively, half a millennium
or a quarter of millennium of history about to turn, about to change.
For five years, on and off, London was bombarded by aircraft
and rockets, killing or injuring a quarter of a million people,
and ripping huge holes in the fabric of the city.
By the end of the war, it was realised that if London was to rise again,
the first essential step on the road to reconstruction
would be to record the damage - all of it.
And the only way to do that was from the air.
Between 1945 and 1949, the RAF flew more than 200 missions over London,
shooting 50,000 individual frames,
recording every square inch of the capital.
Now every single one of these images
has been scanned, and all the scans have been pieced together.
For the first time, we have a comprehensive
aerial picture of wartime London.
The London you're looking at is still
the London that had to, er, it felt it had to be self-sufficient in food.
Virtually every open space is given over to allotments.
Here you can see in front of the Imperial War Museum,
you've got a really quite substantial area just given over
to growing vegetables and so on.
In fact, almost all open spaces in London
were used for cultivating food.
While the parks are full of vegetables,
the streets appear strangely empty.
The only vehicles in evidence
are trams or buses or a few essential trucks.
Barely 10% of Londoners own their own car,
and those that do are kept off the streets by petrol rationing.
These are the details of daily life where the bombs didn't fall.
Where they did, the picture is rather different.
Tens of thousands of buildings, like these riverside warehouses,
were totally destroyed.
If you go across the town, some parts of it are largely unaffected,
but then when you look at it in detail, certainly with the City,
you've got really very substantial destruction -
whole blocks have been basically trashed.
If you look at the area around St Paul's, for example,
you can just see the stubs of the walls which have been left,
preparatory to the redevelopment of this particular area.
Effectively, it looks like the ruins of Pompeii.
And it's not just public buildings that were hit.
A third of London's homes had been badly damaged.
In some areas, 85% of the housing stock had simply disappeared.
1.5 million people had nowhere to live.
It was clear rebuilding would take years,
but there was a desire to do more than just rebuild.
In the ruins of London lay an opportunity
to completely redesign the city.
And there was a plan to do it -
the Abercrombie plan.
As early as 1943, a team of designers under Lord Abercrombie
had begun work on a new city that would rise from the ashes of the old -
a clean-lined, open and thoroughly modern metropolis.
London grew up without any plan or order.
That's why there are all those bad and ugly things
that we hope to do away with if this plan of ours is carried out.
The plan was a top-down reordering of the entire city
that would solve the housing crisis and produce more efficiency.
Down here, near the boundary, would be a trading estate
where many of the people living in the district would work.
The city would be reorganised into zones.
There would be zones for living, zones for working,
zones for retail and commerce.
All these different zones would be connected together
by a vast network of new highways that would speed workers
to their destinations and bring raw materials in to the working city.
Cars and roads would be the way forward,
as Abercrombie had seen in America.
It's a pretty gigantic scheme,
affecting the future of the whole of London.
But this new city would do more than just work better than the old one.
At its heart was a desire for space and order for its people.
For every 1,000 inhabitants, there should be at least four acres
of open green space - roughly twice as many as before.
To liberate that space, much of the housing
that hadn't already been destroyed would be demolished.
And the people in them would be collectively rehoused
in thousands of new apartment blocks, stacked in rows across the city.
Just like Churchill Gardens.
In Pimlico, not far from the Thames Embankment,
a giant skeleton of steel is going up,
the framework of a block of bright, modern flats
that are to transform living conditions in this quarter of London.
This vast housing estate near central London was the first great test
of Abercrombie's vision.
Brand-new homes for over 3,000 people in a single development.
Paul Finch was one of its early inhabitants,
now returning after 40 years to the estate he lived in as a child.
It was quite exciting.
I mean, we came here to go in the playgrounds and to mess about.
Churchill Gardens was the new thing that was being built,
and I think we just accepted it as...this is how it is.
I had a school friend who lived in Lutyens House,
and I can remember standing on the balcony outside his front door,
looking down at a terrace of houses opposite that were being demolished.
I remember his brother saying he wasn't sure why they were being demolished
because people still lived there.
I thought it was pretty obvious why they were knocking them down,
cos they looked really old and dilapidated
and kind of clapped out, compared with all these modern blocks that we now lived in
with hot and cold running water and central heating.
It was the idea of something modern and new and clean.
I think when you look back at films of people who occupied new council housing,
'40s, '50s, even '60s, what you see is people who are very,
very happy with what they've got, and the reason for that is,
which we all forget now, is what they came from.
By and large, fortunately for most people, they don't have to experience
the conditions, certainly, that their grandparents did,
where what we would now regard as basic and essential facilities
were simply not available.
The late 1940s was a radical time, when Britain first turned old ideas
of a National Health Service and a full welfare state into reality.
It was an era that deliberately and unashamedly promised
a brave new world for everyone.
This is Churchill Gardens today.
What's clear is that it's totally different to everything around it.
If this is as far as the housing revolution got,
what happened to the rest of Abercrombie's plan?
The only way to find out is from the air.
Archaeologist Chris Going has been documenting the changing face
of London from the air for the last five years.
We have nine frames on the second run, I think.
By flying exactly the same route the RAF did 60 years ago
to create the first aerial surveys, Chris hopes to create
an identical modern survey of his own.
What we are doing today is we are producing imagery which,
when we compare with the 1945 material, gives you in one go, if you like,
all the changes we've seen in the city of London, in the centre of London,
in the last 60 years.
It's effectively a time machine.
By lining up the two complete sets of images, Chris is able to switch
between the past and the present.
Between the London Abercrombie was about to change,
and what we actually ended up with.
Overall, there appears to be very little difference.
The basic matrix of roads is largely unaltered.
There's certainly no sign of any great unified vision.
If the population of London in the later '40s or the '50s
could look at the London of 2008, of the 21st century, I think
the thing they would most clearly say is how incoherent it looks.
It does not that like the sort of envisaged city
of the planners of the '40s and '50s.
When it came to housing, local authorities never followed
the Churchill Gardens model, but took to building clusters
of high-rise tower blocks instead.
While around them, private housing remained
almost entirely pre-war vintage.
Exactly the opposite of Abercrombie's vision.
The plan to double the total area
of green space in the city produced just one notable south London park.
And the transport revolution that promised fast access
along multi-lane freeways throughout the centre of the city
never reached that far.
Today, congestion blights the motorways running into London,
because the centre is just the same old maze of streets
from before the war.
And in the heart of the city, where a great modernist capital was meant
to stretch along the Thames,
only the centrepiece, the Royal Festival Hall, was ever built.
Ultimately, Abercrombie failed.
But his failure should be judged in the light of history,
because London had tried this kind of thing before.
300 years earlier, after the great fire, Christopher Wren
came up with a grand new vision for London.
A formal European capital that would radiate out
from the glorious centrepiece of St Paul's Cathedral.
But just as with Abercrombie, the centrepiece was all that got built.
Neither man managed to get the money or the political backing
to tear down the city and start again.
Wren had a big vision for London, which he was not able to fulfil
because of the competing interests of people who, basically, just wanted
to get back to what it was like before.
After the Second World War, Abercrombie had a plan.
But London is resistant to grand plans.
Yet London has been transformed all the same.
From the city of the 1940s
to the city of today, there's a world of difference.
And far from following any central plan,
it's largely the result of barely controlled economic forces.
What London responds to is trade,
commerce, money, markets, prosperity and movement.
And in the end, what has made London is precisely those things.
Money changed London in ways no-one in the 1940s
could ever have imagined, because London changed the way it made money,
and nowhere shows this more clearly than here.
The modern, geometric blocks of Canary Wharf now hide what used
to power this city - the docks.
Since Roman times,
London's docks had been the engine room of the city's economy.
Stretching for ten miles along the Thames, by the late 1930s,
the port of London had grown to be the largest in the world.
This was where the whole of the British Empire brought its goods to trade,
which is why, when the war ended, the docks were rebuilt immediately.
Dock workers had to make do with living in prefabs.
And for 30 years after the war, life in the docks went on, more or less,
as it had before, and looked set to continue, unchanged, forever.
What they didn't see coming was this.
By the 1970s, what the world's economy demanded for shipping
was giant bulk containers carried on giant container ships
that could only be processed in giant container ports, like Felixstowe.
None of which would fit into London's tight, narrow river,
with its densely packed, labour-intensive docks.
As the last dock facilities finally closed at the end of the '70s,
the remaining 10,000 jobs went with them,
leaving behind a vast, derelict wasteland.
When the docks became redundant in the early 1970s,
there was a great think about what to do with this area.
There was a public sector body set up, which was going nowhere,
and then suddenly the hand of commerce intervened,
because people who were having a problem
getting sufficient office space in the City of London,
at the sort of rents they thought they should be paying,
suddenly looked at Canary Wharf and thought, "Why don't we do it down there?"
And this great private sector experiment began.
This was the first time in hundreds of years that eight square miles
of prime building land had appeared so close to the centre of London.
There was an unrivalled opportunity to think through
what the whole development would be over its entire lifespan
and to plan for that right from day one.
This was very unusual.
By the end of the '80s, the wasteland had become
the biggest building site in the world.
I remember first arriving here and seeing a forest of tower cranes
and very little else. We recognised that at the beginning
we would have to build a certain number of buildings to start with
just to get people to move here and to realise
that this wasn't just an office building in the middle of nowhere, but a place,
and I think the risk was in creating that first group of buildings
and expecting that companies would actually move here as a result.
Prospective companies were lured by huge Government incentives,
effectively giving the land to anyone who'd build on it,
as well as paying for new transport links
to bring City workers to their new offices.
At first, all went swimmingly.
Then the country was hit by recession and, suddenly,
no-one would take the risk of relocation to a giant building site.
The first Docklands developers went into receivership.
When the economy did finally turn round,
the developers had their master plan waiting.
And the result was this -
what's often been likened to a piece of Manhattan, dropped from the sky.
People say, when they're in Canary Wharf,
"This doesn't quite feel like London,"
and the reason why it doesn't feel like London is because it isn't like London.
And the reason it's not like London
is because it was master-planned by American architects and planners,
working in a tradition of a grid, working, right from the beginning,
with the idea that you should integrate transport
and employment in one seamless way, which it does extremely successfully.
In fact, the only problem it has is maybe it's a little bit too successful,
but that's better than not being successful enough.
Where 100,000 men once handled cargo at the end of the war,
just as many people now earn a living in financial services.
By the turn of the century, this alien-looking invader
had become a serious rival to London's old financial centre, the Square Mile.
The old City was bound to respond to the challenge.
And it has.
This is the Square Mile today, in the midst of a colossal building boom,
the most obvious feature of which is that its jumble of structures
looks very different to the organised blocks of Canary Wharf.
And that's because new buildings here don't stand on a regular grid.
They stand on a street plan that hasn't changed radically
in 1,000 years.
The streets of London, which is really the geography of London,
especially the heart of London,
is rooted in medieval history. They're narrow, and, basically,
they're for horses and people who are walking.
We've kept to that in most areas in the centre.
This gives some pretty big constraints for -
1,000 years later, shall we say - where movement has completely changed.
We don't have the classical streets that you see in Paris,
or the grid forms we see in New York.
We have grown very much ad hoc, piece by piece.
The name of the game here is to squeeze bigger and bigger offices
into these irregular spaces.
One of the best examples of how this can be done is the Gherkin,
which cleverly creates more space in the air than it has on the ground,
with its bulging shape.
Others are twisted into a variety of strange forms
to maximise the limited space they have.
Architecture has developed out of constraints.
The real art of architecture is getting a constraint - you can't avoid them -
and then turning them upside down and seeing how they fit.
But there's more in the City than just a street plan to challenge an architect.
There are dozens of ancient buildings,
none greater than the looming presence of St Paul's Cathedral.
For 350 years, St Paul's has been the jewel
in the architectural crown of the City,
and is now so venerated that even the views of it,
from miles across the city, are protected by planning laws.
Fortunately, there's a new visual tool to help architects avoid the problem.
This picture, and thousands like it, form part of a giant 3-D graphic model
showing the whole city, with St Paul's at its heart.
These are the sight lines,
where the greatest restrictions on building are enforced.
It was in one of these corridors that Richard Rogers was asked
by developers British Land
to create what would be the tallest office block in the City of London,
a structure that would stand right behind the cathedral.
The only way to get out of the view is to slope backwards, out of the views.
So when you're looking, specifically, from the west side of London,
you would block St Paul's if the building was straight up.
So we move it sideways
and you get a sort of A-shape, or, as it's been termed, a Cheese Grater.
This is it - the Cheese Grater,
at 122 Leadenhall - a 225-metre, 48-storey office block,
London's newest skyscraper, as it will look very soon.
What's made this possible is the creative power of 3-D graphics.
Rogers' design partner, Cityscape,
built a virtual 3-D model of the whole of the City of London
and then plonked into it
a millimetre-perfect vision of the Leadenhall Building,
proving, before the first stone was ever laid,
that it would fit into the existing city.
And the Leadenhall Building
won't be the last to make use of this new technology.
Each one of these structures
is set to "grace" the skyline in the next few years.
There must be change, always change,
as one season, or one generation, follows another.
When Lord Abercrombie first proposed building a new city after the war,
it was assumed it could only be done
by tearing down and starting again, with a great plan.
In the late 1940s, people believed in planning,
and they believed that planning was going to create a better London,
a better Britain and a better world.
London did change, but not through grand designs or utopian ideals,
but by commerce and opportunity and the creative energy of its people.
Today, London is the greatest capital in the world.
The only competition is New York.
So it's a big change,
not only in economics, but in social as well,
in the vitality of the city. So that's fantastic.
And it comes out of that marriage of 1,000 years between old and new,
the more formal -
the churches, the town halls, city halls, and so on -
and the wonderful medieval structures and the modern buildings.
So they all sit together.
Not everyone loves the way London is changing,
but London is simply doing what London always has -
making money,
making compromises,
evolving.
Subtitles by Red Bee Media Ltd
E-mail subtitling@bbc.co.uk