It was a moment of casual ruthlessness outside a busy Glasgow supermarket seven years ago that lit the fuse under Britain’s most brutal gangland feud. Kevin “Gerbil” Carroll, a brutal enforcer for one of Scotland’s most notorious organised crime clans, was sitting in his car outside a superstore in the city’s north-east. What happened next will never be forgotten by the throngs of shoppers who witnessed it. Two men approached and fired several rounds into the car, killing Carroll outright in a gangland hit that had been carried out with cold precision.

The intensity of the police investigation into the shooting of Carroll led to an initial period of calm in a tit-for-tat war that had raged through Glasgow’s hardest streets for 10 years. Its origins lie in the rivalry between two family gangs, the Lyons and the Daniels, for control of the city’s heroin and cocaine market.

In the past 18 months though, hostilities have been renewed with an intense ferocity that has led the Scottish government to intervene behind the scenes. There have been daylight shootings outside two primary schools in Glasgow at times of the day when children were being fetched by their parents. In another incident, the driver of a car was shot dead as he waited for the lights to change near a motorway junction.

Earlier this month, Craig Gallagher, reputed to be on the opposite side of Carroll and his Daniels clan associates, was hunted down by unknown assailants to a derelict property in Lanarkshire. There he was believed to have been stabbed before being doused in petrol and set alight. He survived the attack because the building also caught fire and he was able to make his escape in the confusion. He then calmly drove himself to a nearby hospital and asked to be treated.

Gerry Gallacher, a retired senior detective whose beat covered some of the city’s most dangerous neighbourhoods, has since spoken with police sources who were among the first on the scene. “There was a degree of admiration for the professionalism with which the execution of Gerbil had been carried out,” he said. “Nothing was left to chance.”

Even by the ferocious standards of Glasgow’s crime clans, Carroll’s activities were notorious. He had a predilection for deploying power-tools and blow-torches in his day-to-day activity of enforcing the will of his boss, Jamie Daniels, head of the clan that bears the family name. According to Gallacher, he had simply carried out one too many attacks on Lyons’s personnel and thereafter his days were numbered. His fate was probably sealed after the Lyons clan received information that he had violated the grave of a young member of their family who had died in childhood. In 2015, William Paterson, 35, was jailed for life for Carroll’s murder.

Feared gangster Kevin Carroll, left, was killed by William Paterson in 2010. Photograph: Strathclyde police and Rex

Gallacher, who was a policeman for 25 years, is not surprised at reports of government intervention. “What troubles me about this latest round of incidents is the brazen aspect about them. They are happening in daylight and in built-up areas where children and families are present.”

Another former detective said changes in police attitudes to informants have left the force at a disadvantage when dealing with this heightened level of gangland activity. “Individual detectives might spend years gaining the trust of an informant whom they might have managed to groom in exchange for a lighter sentence or early parole. Recently, we’ve been discouraged from getting too close to informants. They’ve been shared around a pool of officers, many of whom will have had no previous connection to the informant. This simply doesn’t work and undid years of knowledge about gangland activities.”

And while surveillance techniques have increased in technical efficiency, so also have the crime clans’ ability to combat them. “Whenever a trial takes place of anyone accused of gangland activity, it’s like a university lecture for the families,” said Gallacher. “You can see them, taking notes in the public benches whenever there are details given in evidence of police techniques. They aren’t stupid.”

The latest surge in gang-related violence has occurred at a time when Police Scotland is suffering a crisis of leadership. Last week it was revealed that the second highest ranked police officer in Scotland, Iain Livingstone, was also standing down amid reports that the entire senior police executive is set to move aside. Senior officers are also under investigation for illegal gathering of data against former police colleagues and a handful of investigative journalists.

Despite billions spent over decades in relaunching Glasgow as a modern and sophisticated city of opportunity and leisure, it has never quite managed to shrug off its legacy of 1930s razor gangs, famously portrayed in the novel No Mean City by Alexander McArthur and H Kingsley Long. In the 1980s, Arthur Thompson, feared and feted in equal measure and a former associate of the Kray twins, was the unchallenged master of the Glasgow underworld. The world he inhabited came to public prominence when his son, Arthur Jr, was gunned down outside his home. Days later, two young hoods, Joe “Bananas” Hanlon and Bobby Glover, were found shot dead in a car that had been dumped at a spot near where young Arthur’s cortege would pass later that morning. Since then, there have been sporadic outbursts of warfare including the notorious ice-cream wars of the 80s.

It’s no coincidence that the crime gangs’ main centres of operation are among the UK’s most disadvantaged communities. The districts of Maryhill, Possilpark, Milton, Springburn and Barlanark form a belt of acute deprivation along Glasgow’s northern urban approaches. Their hearts once beat to the steady thrum of heavy industry and employment was plentiful. When a succession of postwar governments dismantled the industries, a void was all that remained in the absence of any long-term or sustainable replacement.

Officers of Strathclyde police with weapons seized from gang members. Photograph: Drew Farrell/Strathclyde police

In these blasted terrains, the big and hard men offered leadership and a sense of purpose in the absence of anything similar being offered by governments. They offered affluence and status in exchange for unshakeable loyalty and generations of young men whose futures had been snatched away by mass unemployment were attracted by the opportunity to even up the score.

John Carnochan was a detective chief superintendent in Strathclyde police and co-founded the world-renowned Violence Reduction Unit. He has no doubt about the role that poverty and social disintegration plays in young men being attracted to this lifestyle. “You can trace a line of inequality through the communities that the crime gangs operate in,” he said. “If you are a young man who knows he has no future in work but everywhere sees evidence of grossly conspicuous consumption, then of course he wants some of that for himself.

“And if he feels the state has denied him that, he can easily justify helping himself. Especially if he is given a sense of belonging and purpose to a cause he can belong to. These are attributes valued in public life and by governments. It’s time they started to ask themselves why young men in these communities are seeking it in crime. It’s time they got radical about tackling inequality in these communities. It’s about early intervention in very young lives to combat adverse early events.”

It will not have gone unnoticed among Glasgow’s crime warlords that Police Scotland is in complete disarray. The violence won’t be stopping any time soon, nor will the laundering of the profits in all the usual outlets. The leadership and organisation of the family firms currently far outstrips anything that the forces of law and order possess.