The graffiti artists making their mark on the city

It was 19 March, 2003, the night before the US-led invasion of Iraq. As thousands of British troops prepared to launch their attack on Baghdad, four men back on home ground crept through the streets of west London, towards one of the biggest train yards in the city. Here, they planned to paint a tube train – or "whole car" – signed off with the words "We Made Love Not War", as a bold protest against the allied invasion. "It was that hour when the dark of night is surrendering to the day with hints of blue breaking through the sky," recalls Fuel, who led the charge that night. "Everything is still and calm; the roads and the tracks are devoid of traffic. London's still sleeping."

Fuel is one of the British graffiti scene's biggest and most respected players, widely considered a legend by his peers. Now in his late thirties, he has been targeting the city's streets since he was just a boy and the lure of the train yard, he says, is still too strong to resist. "For 16 years I've been painting this same yard," he says. "Now I bring my own son here, to watch the trains as they sleep."

On this particular night, six years ago, Fuel and his men followed the Westway by foot until they reached their final destination: a small enclave above the track from which they could properly survey the scene. Before setting to work, first lowering themselves down towards the stationary trains by rope, the men paused, taking a moment to drink in their surroundings. This quiet interlude, the "calm before the storm", was a time for reflection, a space in which to gather their senses. Carefully drawing a mental map of their intended route, the men accounted for the potentially lethal live third rail, any hidden surveillance equipment and an emergency exit to where their getaway car was stashed, should the alarm be raised. There was no space for miscalculation; nothing could be left to chance.

In recent years, with increased forensic analysis, covert surveillance and targeting of known suspects, the government forces in charge of combating "serious vandals" have mounted a series of operations to tackle these crimes. If caught, illegal graffers – whose work is easily identifiable by the signature or "tag" every writer signs next to his (or occasionally her) piece – face heavy penalties, as confirmed by another high-profile writer who wishes to remain anonymous: "Right now I have five friends in jail and two on bail for 'bombing' [a term for spray-painting] trains and I think every 'writer' in London has had their door kicked in by the graff squad recently," he says.

The increased Government offensive against those who vandalise Britain's trains is a move that has been met, in the main, with public approval. After all, whether you like the end result or not, it will be removed, and this process results in no small cost for the taxpayer. London Underground suggests that repairing the damage caused by graffiti to tube trains alone costs a minimum of £10m each year. Yet, while it would seem that their crackdown has, to some degree at least, been a successful deterrent – with statistics for 2008 to 2009 showing that reports for this type of vandalism to the train network is down by 22 per cent from the previous year, to just 3,328 – there is a considerable pool of "writers" who are prepared to take their chances. The thrill of painting a train, they believe, is worth taking the risk. For the sensation that comes from a successful night in the yard, Fuel explains, is unrivalled by any other. After signing off his piece that night in 2003, as the first signs of morning sun strained through the horizon, Fuel recalls, he feels a rush of pure, unadulterated euphoria: "The train's pulsing, alive with colour," he says. "On nights like these we defy conformity and fear and dance in the flicker of hope."

The private motivations of the graffiti artist and the world he inhabits is one that, according to the photographer Will Robson-Scott, has – until now – lacked proper exploration. And so, for the past four years, Robson-Scott has spent countless nights shadowing some of Britain's most prolific writers as they scale the rooftops and undergrounds of our cityscapes. His images, along with a series of exclusive interviews, are showcased in a new book called Crack & Shine, which offers an alternative view of the capital city through the eye of its "street bombers".

These men, Robson-Scott observes, would not consider themselves street artists like Banksy or Blek Le Rat. They are not interested in the democratisation of art; they don't seek public approval. "The majority of the people featured in this book don't respect people like Banksy," he says. "They see street art as a bandwagon thing, aimed at making money and getting famous." This sort of commercial selling out, he says, goes against the very essence of illegal bombing, which operates outside the constraints of conventional society.

For the street bomber, Robson-Scott continues, the rewards are less tangible; the gratification is – in part at least – derived simply from existing in their own private universe, removed from the mainstream: "Being a writer informs the way you see the world," he says. "It's more than writing on walls. Spaces and landscapes takes on a new meaning, almost every aspect of your life is influenced." Exactly what draws these men to this way of life is hard to put into words, he says: "Some of these guys have been writing for 20 years, but if you asked them why they do it, they probably couldn't give a straightforward answer." In an attempt to communicate the indefinable sense of personal freedom and quiet exhilaration that sucks them in, Robson-Scott seeks to capture the experience of "the unknown city within the city".

"I'm interested in presenting people with experiences they wouldn't otherwise have in their life, showing them how others view the world, offering a new perspective," Robson-Scott explains. "In this case, it is the quiet moments of apprehension that occur before a writer strikes that I want to convey: the feeling that comes while lurking in the shadows, waiting for a guard to pass, or feeling a rush of air as a train flies past two inches from where you're crouched." These are the sensations, he says, that can't be put into words.

'Crack & Shine' is published by FFF London, £30, and can be ordered from the website crackandshine.com