Three decades ago even the police didn’t know what a heroin addict looked like.

“When one came to the charge bar we would all take a peep,” says Kenny Simpson, then a young constable. “They were really unusual creatures.”

When Mr Simpson, now a civilian expert at the Scottish Crime and Drug Enforcement Agency or SCDEA, joined the police in 1978, there were maybe 50 people in Glasgow using the drug.

There were so few, in fact, that the head of Strathclyde Police’s drug squad, Jack “The Flea” Beattie, boasted that he knew every one of them by name.

The Flea – he got the nickname because he could never sit still – finally stood down in 1980, the year smack hit Glasgow.

Within 12 months the city had a thousand addicts. Today it has around 5500, 100 times more than when the Flea was on the job.

Each addict consumes an average of £40 of the drug a day, sustaining an underworld business worth the best part of £100 million a year.

So why did heroin come to Glasgow? “Because drug dealers – and there always have been drug dealers – identified that there was huge profits to be made,” says Mr Simpson.

And why 1980? Firstly, Clydeside had just been hit by the first wave of recession that followed Margaret Thatcher in to power. And secondly, dramatic changes in the Middle East, such as Iran’s Islamic Revolution, meant there was a lot more smack on the market.

One Lanarkshire ‘entrepreneur’ spotted an opportunity. James Rea is widely credited with being the man who opened Glasgow to heroin. He was jailed for 12 years in 1983. But not before he had built a network of street dealers across the west of Scotland, many of them addicts themselves.

“It was the user-dealers who were the catalyst of growth,” says Mr Simpson. “When I joined the police the stereotype of a heroin users was somebody who looked like something out of the sitcom the Young Ones.

“Now the stereotype is somebody from the inner city, whose life is so bad they want to escape, perhaps from mental health problems or sexual abuse.”

Rea wasn’t the only crook to tap in to the misery of the time. Others did too. Their successors are still running Glasgow – and Scotland’s – heroin business.

Mr Simpson says: “I am now dealing with the sons and grandsons of the criminals that I dealt with back in 1978.

“Crime becomes a way of life. It is territory that is protected by families that have been there for years. There are no trading standards, no insurance. Instead, you have horrific levels of violence.”

Back in the 1970s Graeme Pearson, the former head of the SCDEA, was one of The Flea’s men.

Now a professor at Glasgow University, he agrees that heroin transformed Glasgow. But it also, he says, completely re-shaped the city’s underworld.

“There is an old notion that some kind of moral code prevented criminals from becoming involved in drugs. Well, that went within seconds. Once they saw the colour of the money, morality went out the door.”

Prof Pearson remembers tipping off The Flea’s replacement about a kilo of heroin arriving in Glasgow every Friday. The then DCI denied so much of the drug could ever make it north of the border. He was wrong, Pearson was right and the consignment was seized.

The record haul for a single bust in Scotland now stands at 200kg.

One thing that hasn’t changed in Glasgow over 30 years is the cost of a bag. It was a tenner in 1980 and it is a tenner in 2010 – dealers, jokes Mr Simpson, never have change.

Beginning of the end

His death is usually listed as Scotland’s first heroin murder. It wasn’t the last.

Robert Kane, a dealer, died in October 1982, stabbed in a Maryhill flat.

His supplier, William “Toe” Elliot, thought Kane had been cheating. So he and another thug, Ronald Neeson, took Kane’s life.

Elliot was to spend 17 years in jail. Glasgow’s gangs have been fighting drug wars ever since, as gangsters – and Toe was one of the hardest – vie for control of the market.

Police believe they have managed to suppress some of the violence. Glasgow, for example, had fewer shootings than Edinburgh last year.