But Grieve also had flair best summed up as a combination of curiosity lateral agility and shrewdness

But Grieve also had flair, best summed up as a combination of curiosity, lateral agility and shrewdness. He was soon absorbed into the detective force and, by the early Seventies, was on the Drug Squad, tracking the misdemeanours of his counter-cultural contemporaries: there are plenty of now-respectable media figures who were stopped and searched for acid and marijuana by John Grieve in their wilder days; at the time, they say, he looked exactly like any other street hippy with his long hair, scruffy jeans, windbreaker and plimsolls. He shared some, if not all, of their tastes and is still a fan of the Rolling Stones, Bob Marley and Eric Clapton, all them at one time substance abusers. He ran a clean ship, but this was a time of open distrust between Customs and the drug squad, with the former believing - with justification - that some of the police were corrupt.Drugs, and their corrosive effects, became a speciality, perhaps an obsession, but Grieve also worked in the Flying Squad and on murder investigations, and has done his time in uniformed commands around the Metropolitan area. (In 1979, the police sent him to Durham University, where he read Philosophy and Psychology, a choice he disguised from his senior officers until the last moment; he took his M Phil at Cranfield.) When I asked him what was the most destructive force in British society, he answered without hesitation that it was drugs and poverty, the latter being responsible for a great despair and acting as a catalytic agent to the former.

As a policeman, it is the drugs problem that he is concerned with and the insidious effect it has on other areas of crime. "I would single out drugs because it has great moral dilemmas and presents us with the most acute intellectual challenges - the use by criminals of banking systems for money laundering, the worldwide influence of drug smugglers It is a social problem of such complexity. Every answer has a big down side."Among those answers is legalisation, and Grieve has had his fingers burnt by musing on this. (In May 1993, he urged the Association of Chief Police Officers to "think the unthinkable", and to consider the licencing of some drug dealers.) "I teeter between being acceptable and being a maverick. I am out of the debate at the moment because I want to be supportive of the present strategy [that is, nailing dealers and trying to track their supply lines]. But one of the things that should be made clear in the legalisation argument is that legalisation can mean that people live their lives with their minds blown out by drugs - the sort of effect you see in the hill tribes of Thailand."What has changed the complexion of crime is the money generated by drugs It drains down into everyone's lives.

We say it is probably only seven handshakes from the street deal to the highest level of criminality and the violence associated with the recovery of debts. The violence bleeds into society." (Grieve once said that "You are more likely to be offered drugs for the first time by a member of the family or a close friend than by the archetypal stranger at the school gates. When parents demand we arrest the dealers, it is their own children they are referring to.")When Grieve was appointed to SO11, he was told by a senior officer to be "lawfully audacious" He took the first word to heart. Without my prompting, he brought up the Porn and Drug Squad scandals of the Seventies and Operation Countryman, that era's investigation into corruption in the Met, all of them immensely damaging to the reputation of the police. He agonises about this: "There is a lot of thinking about what moral risks there are. Dostoyevsky explored it, so did Ruth Rendell, and there was a Commanding Officer called Jim Barnett who wrote a series of novels after he retired - he said we let police officers loose into a moral minefield.

So when I went to university I used my thesis to tease out what the issues were. By that time, I was in my mid-thirties and I had been in the Drug Squad and I knew all the players in the Porn Squad scandal. I came back for the second big Drug Squad scandal and for Countryman."I said that these scandals did not seem to be exactly the topic of the moment. Why did they weigh so heavily on him?"Maybe I am peculiarly sensitive," he said, "but you see we have just got through a whole series of problems about informers who turned out - surprise, surprise - to be criminals who were still committing crimes. In a court of law, the defence says there is more to it than that. I am not saying that the problems are still the same as they were; I am saying that if you lived through that period you are very conscious of that aspect." Grieve, of course, was referring to to the SO11 operation to protect Eaton Green, a Jamaican/Yardie informer who is now serving six years for his involvement in the hold-up and robbery of a blues party of 150 people in Nottingham.