Police knew there was major drugs supply chain in West Watford called the Khan Line years before slapping handcuffs on its ringleaders.

Yet it was only through a dangerous undercover operation that police finally pieced together who was behind the crack cocaine and heroin network blighting the town.

In an interview with the Watford Observer, Detective Inspector Tannis Perks, who led the team which smashed the gang, described the police operation which snared one of the town’s most prolific drug supply rings.

She said it was a series of arrests of low-level dealers in 2010 that gave officers their first real sniff of the operation in practice.

It was clear that the vulnerable and often young drug couriers picked up by police in West Watford were not organising themselves.

From that point the officers decided to launch an operation to uncover and take out those controlling the Khan Line.

“We knew whoever was running the Khan Line was causing a lot of misery for a lot of people,” said DI Perks.

From September 2010 undercover officers worked to build up a picture of how the operation was run.

They discovered that all calls came through to a single pay-as-you-go number, which was receiving in excess of 100 a day.

A member of the Khan gang was allocated responsibility for the phone at the beginning of the day and line was open for business as soon as it was switched on.

When calls came through drug users would order using slang such as “brandy” for heroin of “whisky” for crack.

DI Perks said once an order had been placed the caller was given a location for the pick-up.

The Khans would then contact a street dealer and direct them to the location with packages.

Both the locations and dealers chosen were at random to keep police from establishing a pattern and keep the Khans at arm’s length from the transactions.

The gang would also frequently change the house from which they operated to avoid police.

DI Perks said: “They picked on vulnerable individuals and took over their houses. They would turn up with the drugs phone and commandeer the house to run the line from.”

The service was only open to buyers the Khans knew or those whom had been vouched for by people they trusted.

The undercover work needed to get officers close enough to buy from the line was exhaustive and treacherous.

“It is a very stressful environment to work in for undercover officers, being on the ground and at risk of being compromised,” added DI Perks.

However undercover police managed to buy drugs from using the line numerous times - to the point where some of the Khans themselves sold directly to the officers.

During the operation police amassed other evidence linking the Khans to the drug dealing, including records of them topping up the Khan Line phone with credit and finger prints on drug packaging.

DI Perks said when she and her team felt they had enough to evidence they consulted with the Crime Prosecution Service.

The result was that in June last year 150 police raided 11 addresses across West Watford including in Whippendell Road, Euston Avenue and Durban Road West.

DI Perks said officer found drugs and cash and the gang members offered little resistance to the police.

Following the sentencing of the gang’s leaders, DI Perks added: “It is an absolutely cracking result for us, we are really, really pleased.

“I am sure many people in the community thought they were untouchable and they thought they were untouchable, but they were not as clever as they thought.”

On Monday ten members of the Khan Line gang were sentenced at St Albans Crown Court :

Arfan Khan, 27, of Durban Road West – sentenced to 9 years

Ahsan Khan, 25, of Durban Road West – sentenced to 7 years

Umar Khan, 31, of Trinity Hall Close – sentenced to 9 years

Simon Alcott, 41 of Wiggenhall Road– sentenced to 4 years

Lloyd Clarke, 22, of Euston Avenue – sentenced to 4 years

Jabraan Azlam, 25, of Charlock Way – sentenced to 4 years

Kazim Khan, 21 of Rose Gardens – sentenced to 5 years. (Plus 2 years for offences committed while on bail)

A 16 year old boy from Watford – sentenced to a 2 year youth rehabilitation order

Hussayn Naqvi, 18 of Longspring – sentenced to 2 years. (Plus 2 years concurrent for other offences committed while on bail)

Scott Messenger, aged 21 and from Broadfield Road in Hemel Hempstead – sentenced to 12 months suspended for 2 years

Four others were sentenced in connection with the Khan Line at an earlier hearing:

Attar Khan, 29, of Trinity Hall Close was fined £65, court costs of £85 and £15 victim surcharge

Lukan Briggs, 37, of Whippendell Road, received a community order of 18 months

Daniel Frame, 31, of Upper Lattimore Road, received a community order of 1 year with 80 hours unpaid work

Susan Armstrong, 44, of Whippendell Road, received a community order of 18 months