But as I drove under a railway bridge, hoping to see Gentleman's building come up on the right, I was forced to come to a stop. Ahead of me, police vans were parked on both sides of the road and lines of bright yellow scene-of-crime tape ran across it with a sign below saying POLICE NOTICE: ROAD CLOSED. A cluster of onlookers had gathered round the outside of the cordoned-off area, looking excited, while a group of men and women in top-to-toe white suits were trooping in and out of a clapped-out building with sludge-grey paintwork.

I knew without checking the number that this had to be Gentleman's place. And, like everyone else, I've seen enough crime programmes on the TV to know that the presence of this many police, particularly the ones in white suits, means that something extremely serious has taken place. Like murder.

As I sat staring at the scene, trying to take it all in, a uniformed cop approached the car, waving at me to back up. Heeding his instructions, I turned round and found a parking spot further back the other way before returning on foot, looking round for any sign of Tina.

I tried her number again. Still off.

'Do you know what's happened here?' I asked a couple of overdressed old ladies who were tutting and shaking their heads as they watched the police at work.

'Murder,' growled one. 'Some poor sod killed in his own home.'

'Just keeps getting worse,' said the other, continuing to shake her head. 'You wonder when it's all going to stop.'

'They should hang 'em,' said the first lady. 'Bring back the death penalty. That'd sort it out.'

I thanked them and walked round the scene-of-crime tape and through the onlookers to the other side of the street. But still I couldn't see Tina. I went to the top of the road, checked the parked cars. They were all empty.

Where the hell was she?

I looked at my watch. It was nearly six p.m. More than three hours since we'd last spoken; two since the time she'd told me she'd ring. The sun's rays were weakening as evening began to draw in, and I got a leaden feeling in my gut.

Maybe I should have gone to the police there and then. In hindsight, it would have been the best move. But what stopped me once again was the fear that they wouldn't believe me, particularly my story about Ramon, and that I'd end up a suspect, even if I showed them the photos I had.

Instead, I decided to turn to the one man I'd avoided throughout all this. The subject of my book Enforcer, and my last resort.

Maxwell.

Five years earlier, not long after Mike Bolt had joined the National Crime Squad, the organization that became SOCA, he'd found himself involved in a case that had ended up having a lasting impact on him.

It started when a three-man gang of Jamaican thugs based in Dalston took to holding up drug dealers at gunpoint and relieving them of their product and their money. These men were extremely violent and, on the one occasion they did meet resistance, they shot the dealer dead and seriously wounded his bodyguard, sending out an ominous message to all those who might defy them. In fact, so successful did they become that for a short while the supply of crack and heroin in the borough plummeted as the other dealers moved out to safer areas. The gang's luck, however, was always going to run out, and when they robbed two crackhouses belonging to Nicholas Tyndall, a high-level gangster in neighbouring Islington, getting away with tens of thousands in cash and drugs, it finally did.

Tyndall was not the type of man to let such blatant disrespect go unpunished. Because he had a great deal more power and influence than the dealers the Jamaicans had robbed in the past, it hadn't taken him long to identify them. Incredibly, it seemed they weren't even making much of an effort to hide their crimes, clearly thinking they were above retribution.

This changed when one of their number, Ralvin Menendez, was found dead on waste ground near his home, a bullet in his head and his severed penis and testicles stuffed into his mouth. A week later, a second member of the gang, Julius Barron, was discovered at home dead in bed, in exactly the same condition.

The two men's deaths generated only minimal publicity. Drug-related murders within the black community were common, and even though these killings were particularly brutal, there was still little that set them apart from the many others that occurred that year in London.

This all changed a month later when a third robber, Clyde Jones, met the same fate as his cohorts. Because when the killer turned up at his flat, breaking in through a window, Jones wasn't in there alone. Also present was his twelve-year-old niece Leticia, whom he was looking after for the night. No one knows for sure the exact sequence of events but it seems likely that Leticia came out of her bedroom and disturbed the killer as he was in the process of castrating her already dead uncle. If she screamed, no one reported hearing her. It was unlikely she got the chance. She was shot once in the head from a distance of about ten feet, and then twice more in the heart at point-blank range, so it was clear that the killer had deliberately finished her off.

In the ensuing public outcry, the National Crime Squad was called in to find the killer. Bolt had been part of the investigating team, and he remembered all too vividly visiting the Jones flat, a cramped, untidy place on the sixth floor of a tower block whose only views were of other tower blocks. There was a huge bloodstain on the living room sofa where Jones himself had died, and a smaller one on the threadbare carpet outside the bedroom where Leticia had breathed her last. Bolt had thought it such a cold, lonely place for a child to die. He'd been a police officer long enough to know how hard and unjust the world could be, but even so he'd been affected by what he'd seen, and he'd sworn then and there that he'd do everything in his power to find the person responsible.

With a reward of £50,000 on offer, the name of Nicholas Tyndall had quickly come up and the NCS had subsequently bugged his palatial Islington home. Listening in, they heard Tyndall refer repeatedly to someone he called Hook as the hitman he'd used for the murders of all three of the Jamaicans. It sounded like Tyndall was extremely annoyed that Hook had killed a civilian, and was even thinking about holding back on the balance of his payment because of the heat Leticia Jones's murder was generating. No one knows whether or not he did because shortly afterwards Tyndall ordered a professional bug sweep of his property which turned up all the listening devices. Incredibly, even with Tyndall's taped admissions, the CPS had somehow concluded that there wasn't enough evidence to charge him with anything.

Instead, NCS efforts were channelled into locating the mysterious man called Hook, and Bolt's team was given the task of finding out his real name. It took a hell of a lot of digging but eventually they identified him as one Michael James Killen, a thirty-seven-year-old former IRA gunman who was suspected of killing as many as eighteen people in a career spanning almost two decades. Having been released under the terms of the Good Friday Agreement from the Maze prison in 1999, where he'd been serving a life sentence for the murder of two RUC officers and a British soldier, he'd headed to the UK and become a gun for hire within the burgeoning London underworld, where reliable killers were always in demand.

Hook was spoken of with a quiet awe by those few in the criminal fraternity prepared to talk about him. It wasn't just that he was brutally efficient, with a breezeblock for a heart and a reputation for taking on any job and getting it done. There was also an air of real mystery about him. The son of wealthy Belfast accountants (father Catholic, mother Protestant), he was hardly your typical IRA gunman, and was remembered in the movement as someone who was more interested in the thrill of violence than furthering the cause of Irish unification. At one time he'd apparently been a good-looking man, but in 1991 he'd suffered extensive shrapnel injuries to his face and body when a bomb an IRA colleague had been working on exploded. He'd also lost two fingers on his left hand, hence the nickname: Hook.