BEFORE I meet the supergrass Paul Grimes, I must meet his minder. He’s not what I expect: he’s big, burly and shaven-headed, certainly, but the brightly coloured scarf lends him a vaguely academic air. The rendezvous is Liverpool’s Lime Street Station, but the photographer is late and this sends the minder into a mild panic. "Paul gets jittery if things don’t go exactly to plan," he says. The minder then hits one of his two mobile phones and, in a voice muffled by his hand, tries to reassure Grimes that everything is cool. Eventually the snapper shows; he’s a Liverpudlian, too, and he and the minder are soon getting on like a Scouse house on fire, gabbing about Caravaggio, as you do. On the train ride to the suburb of Kirby, the chat turns to the city’s Year of Culture in 2008 and the local heroes they’d like to see being celebrated. Terence Davies, the film director - yes. Our Cilla - no. This is good, it has calmed down the minder, but the tension of the day quickly resurfaces. "Paul was going to meet you in a caf, but cafs are too enclosed..." The 53-year-old Grimes is an old-school gangster, erstwhile leader of the Hole-in-the-Wall gang and Liverpool lieutenant of the Kray twins, who turned informant after drugs became the currency of the criminal classes and heroin killed his son, Jason, on his 21st birthday. But since he helped bring down two of Britain’s biggest dealers, the underworld has sworn revenge. There is a 100,000 contract on his head and there have been several attempts on his life. The train is full of Cilla’s mucky kids and they scamp around in shellsuits until the short journey is over, when the minder gets back on the phone to announce our arrival. "Where are you? Where? Now don’t you be doing your Walter Mitty act again…" A dark-blue Peugeot is parked, with a bullet-headed man at the wheel. One of the few contemporary pictures of Grimes in a new book about his life and crimes has him peering shiftily through a rearview mirror. I recognise the big specs from it and take the driver to be him. "Hello, Paul," I say. He doesn’t answer, and shakes my hand without turning round. Grimes drives off, reaches regulation speed and sticks to it, indicating at every junction. We cruise past the Irby Public Library, then Irby Ironmongers and Irby News. I ask if we’re in a neighbouring suburb with an uncannily similar name. Silence. "Kirby," says Grimes finally. There must be a joke about a notorious shop-sign thief who’s nicking only Ks, but I’m not going to be the one to crack it. We reach our destination, the Wirral Country Park. "Tea," says Grimes, and his minder scurries off in the direction of a hut. Grimes gets out of the car and heads for the picnic area, with its fine views across the Mersey to north Wales. In his polyester leisurewear and trainers, he looks no different from the other dads playing football and flying kites with their children. As I head after him, I spot the folder jammed into the car dashboard. The cover reads: "Safety & Security". How safe and secure do I feel today? Thinking about the bit in the book where Grimes describes how he beats up a man in a pub, using his head as a football, and leaves him for dead, all because the poor fool interrupted a game of darts - not very. He is no stranger to violence, and although he claims never to have killed anybody, there are people out there who want him rubbed out. But my feelings are not important. Grimes is the one who must be comfortable in his surroundings, and today he’s decided that green and pleasant parkland constitutes minimum risk. "If someone wants to have a go, hopefully I’ll see them first," he says, with his minder now back by his side. The poster on the noticeboard next to our bench advertises a forthcoming talk: "In Search of Woodpeckers." Five minutes in, and this is already shaping up as one of my strangest-ever assignments. Words are easily misused and overused. Every model is a ‘supermodel’ and every group a ‘supergroup’, when the latter term properly means a rock band made up of musicians who are already stars in their own right. But Grimes can surely claim ‘supergrass’ status because of the villains he helped put away. When Curtis Warren was finally captured, The Guardian reported that, compared to him, the Krays were "pathetic minnows". Ditto the Great Train Robbers and the Brinks Mat gang: "The plain fact is that Warren is the richest and most successful British criminal who has ever been caught." Another phrase which has lost its impact through becoming lazy, common parlance is ‘dead man walking’. A TV football commentator used it the previous night about the under-threat Chelsea manager Claudio Ranieri, and Grimes and I share an edgy laugh about this. Well wrapped up against the stiff breeze, but with gold chains and tattoos still visible, he tells me a bit about his life as a marked man. Only a bit, though - apart from his favourite sign-off, "It’s one o’ them, intit?", you could never accuse him of over-using any words. He cannot stay in the same place too long. Through the witness-protection programme, the police have provided him with a flat in an OAPs’ tenement block. Sometimes he stays with trusted friends - a different one every night - but at the moment he’s sleeping in a caravan, suggesting there’s no such thing as a "safe house". Six times in the past four years, Grimes says almost matter-of-factly, someone has tried to kill him - and these are just the attempts he knows about. Once his flat was fire-bombed; on another occasion, pensioners spotted three masked men outside and raised the alarm. "It’s one o’ them, intit?" he says. "Luckily I’ve always been somewhere else. The police have foiled whoever was after me and I’ve found out about it later. I’ve got to watch my back, watch where I go, watch who I talk to. There are people out there who respect what I’ve done, but there are plenty others who don’t." Divorced and cut off from his youngest son, Heath - when he brought down the drugs baron John Haase, Heath went too - Grimes jokes that his main hobby is trying, and failing, to quit smoking, and with that he sparks up a cigarette. "I used to go to the gym but you can get shot in gyms," he adds. I say it sounds a pretty desperate existence, checking with the police every day, living in constant fear, but he just shrugs. "Everyone thinks I must be terrified, but I’m not. At the end of the day, we all die." Today, every bustle in the hedgerow causes Grimes to jump. Then the minder jumps, then me. His book, entitled Powder Wars and penned by a tabloid journalist, is requiring him to blow his cover - he recently lost his job as a 6-an-hour security guard after his bosses found out about his past - and it’s easy to be cynical about his reasons for agreeing to its publication. He needs the money? In his heyday he loved fast cars, loose women and sharp suits, and thought nothing of blowing 1,000 on a Chinese meal. But after reputedly making millions from crime he says he’s now penniless. He wants the notoriety? Possibly, but on today’s nervy evidence, he doesn’t have the personality of a ‘Mad’ Frankie Fraser. But he insists he’s decided to tell all in print for the same reason he became a supergrass - to expose drug-dealers. For Grimes, crime was in the blood. At the age of ten, and still in short trousers, he was recruited as a decoy into a firm of professional shoplifters run by his grandmother, Harriet Mellor, nicknamed ‘The Fagin’, who sat at the head of three prominent Merseyside crime families. "It was a way of life, he says. "The bottom line was, you had to put food on the table and back then that was our way. It’s one o’ them, intit? But we weren’t like shoplifters now; they’re just smackheads who steal to get gear. They’re not professionals." This is a familiar Grimes refrain, and he genuinely does believe that in the old days there was honour among thieves. Dick the Stick, Bob the Dog, Johnny One-Eye, Chris No-Neck, Snowball… the first half of the book is a blizzard of crime monikers and crime capers. In the early 1960s, not every teenage boy in Liverpool was trying to squeeze into The Cavern to catch a glimpse of the Beatles - Grimes was busy learning the art of safe-cracking. His uncle, Billy Grimwood, who wore a tuxedo everywhere, claimed the distinction of being the first hoodlum to use thermal lances to burrow through a strong-room door. During the post-war manufacturing boom, England’s north-west was the ‘warehouse of the world’ and new motorways were opening up virgin territory for the Hole-in-the-Wall gang, who at their height were carrying out three raids a week. TVs, tinned ham and, later, Tacchini sportswear for the burgeoning soccer-casual movement - you name it, they nicked it. "I was an adventure capitalist," says Grimes. At different times, according to the book, Grimes thought he was Scarface and Jimmy Cagney, but drugs changed everything. He wasn’t averse to the odd spliff while listening to Pink Floyd’s Dark Side of the Moon, but when lifelong associates started dealing in heroin and cocaine during the 1980s, he claims he had a crisis of conscience. "My main motivation was that these scumbags were killing people. For the first time in my life I was actually facing up to the fact there were victims of crime." Jason was one of them. "Nothing had ever sledge-hammered me so hard," says Grimes of the moment he found out his son was a junkie. He had high hopes for Jason, who disavowed his dad’s lifestyle to enlist in the navy. "I blamed myself - this was payback for my sins; crime karma come back to haunt me." Grimes amassed 38 convictions in his career, mostly for theft, so was often an absent father. "I had inflicted loss and pain on society all my life and that was society getting paid in return. Jason never wanted for anything, but maybe that wasn’t enough." By then vaguely ‘legit’ through scrapyards and a waste-disposal business, Grimes vowed to topple the Liverpool villains who had seized control of drugs trafficking in Britain and turned grass to become a registered informant for the Customs & Excise, codename ‘Oscar Wilde’. Curtis Warren, whom Dutch police reckoned was worth 1 billion, was smuggling cocaine into the UK from Colombia’s Cali cartel, while John Haase had set up the ‘Turkish Connection’, a smuggling route supplying heroin from Afghanistan. He infiltrated Haase’s gang to become a right-hand man but with Warren he got lucky. A 500kg load of cocaine from Venezuela had been concealed in X-ray-proof lead ingots and it was the job of his old accomplice, Snowball, to bury the ingots in a demolition site. But greed got the better of Snowball when he double-crossed the cartel and tried to flog the lead to Grimes for scrap. "Someone had to stand up to these pricks," says Grimes, who also played his part in the seizure of record hauls of narcotics worth 230 million - but it was all done at some personal cost. Jason’s brother Heath went off the rails after he died, according to their father, and laughed off his attempts to persuade him to go straight. It’s obvious that Heath is now pretty much a no-go area for Grimes. He was jailed for five years and, when he got out, allegedly warned his dad to start wearing a bullet-proof vest. "I told him it wasn’t cold enough for one." The Scouse wit hasn’t deserted Grimes yet but now it’s time for him to go. He’s been sitting in the same spot for less than an hour but that’s way too long. His polystyrene cup has been picked to bits and it’s a safe bet his nerves are going that way, too. "It’s one o’ them, intit?" he says of his extraordinary life, and wanders off, his pace quickening with every step. The minder shares my journey back to the city centre when he reveals himself to be the sidekick of the investigative reporter who wrote the book. He’s talking about their next assignment - subjecting security arrangements for this summer’s Olympics to rigorous testing - when his phone rings. In the excitable babble, he mentions RPGs - rocket-propelled grenades. "We’re going to smuggle them into Athens," he beams. It’s just about the scariest thing I’ve heard all day. • Powder Wars is published by Mainstream (9.99)