Compare the settings of White Teeth and London Fields.
Both of the novels use London as their setting, but the same city is presented in radically different ways in either novel. In White Teeth, the emphasis is on presenting London as the multi-cultural capital of Britain. Smith deliberately highlights the way in which so many different cultures all collide and mingle together, creating a mish-mash of sounds, sights and colours. Note for example how Willesden is described soon after Alsana and her husband move there:
Mali's Kebabs, Mr Cheungs, Raj's, Malkovich Bakeries--she read the new, unfamiliar signs as she passed. She was shrewd. She knew what this was. "Liberal? Hosh-kosh nonense!" No one was more liberal than anyone else anywhere anyway.
Note how the signs advertising the shops clearly point towards a multicultural London, even if Alsana does not believe that this multiculturalism is representative of more liberal attitudes.
In London Fields, on the other hand, the shadowy and nebulous setting deliberately paints a much darker and more sinister picture. Note how Samson Young describes the new London that this dystopian novel presents the reader with:
Things have changed, things have remained the same, over the past ten years. London's pub aura, that's certainly intensified: the smoke and the builders' sand and dust, the toilet tang, the streets like a terrible carpet. No doubt there'll be surprises when I start to look around, but I always felt I knew where England was heading. America was the one you wanted to watch...
Note how some of the more negative aspects of London as a city have become exacerbated in this novel set in the near future, and the setting of London is very definitely associated with a more negative impression; London is a place of mystery, a place of dirt, grime and darkness. The metaphor, comparing the city of London to a public house is one that creates a somewhat shabby, dilapidated impression of the setting. Amis and Smith therefore paint a very different picture of London in their novels to highlight their own purposes and themes.