Pearson decided to go after millionaire criminals - and top of his list was Jamie "Iceman" Stevenson.
The drug gang boss, of Burnside, Glasgow, was prime suspect in the killing of his former best man Tony McGovern.
Stevenson's ally John "Piddie"
Gorman, of Irvine, Ayrshire, was also targeted.
Over four years, it led to s61million of drugs seized, 72 arrests, guns found and s2.2million of assets frozen. Both crooks were jailed.
JAMIE STEVENSON had an uncanny knack of disappearing whenever police showed any interest in him.
No one seemed to know where The Iceman went or what he was up to. This also upset the crime clans, who liked to keep tabs on each other.
It made it difficult for the agency to profile him. Many people would have decided he was too difficult to target and picked an easier challenge.
John "Piddie" Gorman, on the other hand, was a traditional criminal. He kept a high profile and was quick to show off his affluence, enjoying a luxury lifestyle built on crime.
In court, he claimed to be a builder. But in years of surveillance we never saw him visit a building site or look as if he had been working on one.
His lifestyle was the envy of other criminals but it was built on the misery of thousands of Scots. His success made him a role model for youngsters, so I was keen to make him a target.
Both men became highly conscious of police tactics and engaged in a series of gang meetings to discuss what the police might be doing.
Those attending the meetings were particularly sensitive about strangers, challenging innocent members of the public and searching for radio equipment and anything that might identify them as police.
We were never discovered but officers did watch with amusement as the criminals went about security checks.
On one occasion, Stevenson believed workmen in his street were police and arranged checks to confirm their identity.
He never knew we were watching him trying to watch us, as he was watching them.
During these years, Stevenson became increasingly withdrawn and spent a great deal of time disposing of, transferring or acquiring legitimate assets.
Stevenson, along with his stepson Gerard Carbin, was channelling money into a fleet of taxis as well as property development. By this time, we had bugged a number of places frequented by Stevenson and agency officers listened to his conversations for months to try to work out his next moves.
It became clear he was trying to clear his decks and prepare for his defence against a prosecution. He even tried to arrange a psychiatrist as a defence witness.
But Gorman was impatient for his next drug import.
Watched by us, he made contact with Douglas Price.
Price was a sea captain with a dubious background and, by the turn of 2005, he was under constant surveillance. When Price headed to Europe, the game was on - something was about to go down.
At this stage, it would have been easy to have taken fright but I authorised agency officers to travel to mainland Europe.
Having been in for a penny, we now had to spend many pounds.
Agency officers were sitting around Europe waiting for the action to start. I knew all our staff felt frustrated but I also knew the targets had been very successful because they had taken great care to ensure their own security.
At the same time, I was coming under pressure from administrators about costs. The bureaucrats were uncomfortable because they did not have direct and detailed control of the agency. But if they had control, the effectiveness of the agency would be severely tested.
They wanted to control the agency without accountability but there was no way I would allow that to happen. Price eventually embarked on a voyage to Scotland in a fishing boat laden with cannabis.
In the end, we had to rescue the crew. They were so greedy they overloaded the ship with eight tonnes of cannabis resin with a street value of s24million.
Meanwhile, another agency team was gathering information on Stevenson and his group who, although connected with Gorman, operated separately.
Stevenson and his gang met to assess any damage caused by police infiltrating his operations.
Unfortunately for him, he could find no evidence of what we were up to, although he knew we were after him.
Once again he disappeared but we now knew where he was heading because we had traced his Dutch bolthole.
We had him - we merely had to wait for the paperwork and evidence to come together.
Operation Folklore came to a dramatic conclusion in September 2006 when 60 agency officers supported by a similar number of officers from Strathclyde Police raided 15 houses and businesses in Glasgow, East Kilbride and Holland.
Money-laundering charges were proved and assets recovered by the Crown. Stevenson and stepson Carbin were arrested with several others.
Stevenson wilted before chapter after chapter of evidence, offering interrogators no response. At one stage on his way back to the cells, he muttered: "I'm f***** here, aren't I?" He was right.
On April 26, 2006, Gorman was jailed for 12 years at the High Court in Glasgow for supplying heroin, cocaine and cannabis worth s362,000 and laundering s178,125.
Stevenson was jailed for 12 years and nine months for laundering drugs cash.
His conviction sent a shockwave across the underworld.
One prominent criminal told police: "If you can get to Stevenson, you can get to any of us."