Police launched an operation to reassure "intimidated" businesses after youths followed murder detectives investigating the killing of an aspiring rapper.

Officers probing the fatal stabbing of Mujaahid Wilson in March faced a “wall of silence” with potential witnesses reluctant to speak out.

The 20-year-old, known by friends as Tiny Sneaky, died of a single stab wound to the heart following a fight outside a pizza takeaway in Thornton Heath High Street on March 14.

Superintendent Des Connors, of Croydon police, said: “What was apparent from the businesses down there, as well as, disappointingly, the murder team themselves, was that when they were down there doing their enquiries they were getting followed by youths.

“They felt quite intimidated... the shopkeepers wouldn’t engage with detectives because they could see these gangs standing outside their shops.”

Detective Chief Inspector Will Reynolds told the Croydon Guardian in April that police were “struggling with people who have seen things not coming forward”.

He added: “What we’re coming up against is a bit of a wall of silence around two distinct groups: people who were with my suspect, and members of the public.”

In the weeks after the murder police launched an operation intended to reassure people in the area and calm fears about reporting crime to the police.

The five-week Operation Heath has also brought an increased police presence to the district centre and led to nearly 100 arrests.

Supt Connors said: “The feedback we have had from a lot of businesses and residents in the area is they are really pleased that there has been quite an overt police presence up there.

“I am not saying there is no longer a problem in Thornton Heath, but in terms of people being intimidated and even a murder investigation being hampered by groups of youths standing outside watching, the operation has certainly made a difference.”

Police made 98 arrests, executed 163 stop-and-search warrants, issued 39 dispersal orders and seized 11 weapons, one of which was a loaded handgun, during the operation.

There were 16 fewer people injured in assaults and seven fewer victims of grievous bodily harm than in the six weeks previously, according to police.

Supt Conners, who led the operation, said he hoped communication between officers, businesses and the public would lead to continued reductions in crime levels.

He added: “We have a community tasking team which is tasked with looking at problems in various wards in the borough and they were given the remit of engaging with youth gang crime and trying to reassure people in the Thornton Heath area.

“I really want to put more of a focus on the local communities and what their real concerns are, not what we think their concerns are.”

Chief Superintendent Andy Tarrant, Croydon’s borough commander, added: “People have actually contacted us to say we have made a big difference, so from our side it has had a really positive result.

“Usually we respond to calls and we might make an arrest, but these were proactive arrests so that is officers going out patrolling and targeting particular individuals and areas.”

A 17-year-old boy was charged on Tuesday with Mr Wilson’s murder and is due to stand trial in December.

The teenager, who cannot be named because of his age, appeared at the Old Bailey yesterday.

He was remanded in custody.