Harrow's most senior policeman has admitted: "Tragically, we didn't do enough to prevent Hassan Kul's murder."
Borough commander Chief Superintendent Richard Walton spoke at a community meeting held yesterday evening about the fatal stabbing of Hassan Kul Hawadleh at High Weald Service Station, High Road, Harrow Weald, on Thursday last week.
It was confirmed that the killing of the 19-year-old student from Colindale, north-west London - who would have celebrated his 20th birthday on March 12 - was an escalation of attacks.
Chf Supt Walton said: "We were aware of incidents and were concerned about the level of violence but tragically, we didn't do enough to prevent Hassan Kul's murder."
He revealed that an emergency power which allows officers to stop and search anyone for offensive weapons in Wealdstone, without needing a reason, was actually introduced on the morning of death of Mr Hawadleh, a former Alperton Community School and Harrow College student who was studying for a construction management degree at the University of East London.
Last night's meeting at the Sri Lankan Muslim Cultural Centre in Whitefriars Avenue, Wealdstone, heard from Acting Detective Chief Inspector John Oldham, who is leading a team of 35 detectives in cracking the case.
He said: "This murder will be solved. I have no doubt about that.
"This event was an escalation by a group of nasty individuals who are hellbent on causing trouble.
"The people involved with this were criminals and a group of criminals that come from a variety of backgrounds.
"We have been very successful so far and this investigation has been quick and wide ranging."
Four arrests have been to date: a 20-year-old man on Sunday, February 22, on suspicion of murder, a 22-year-old man on Tuesday, February 24, on suspicion of assisting an offender, a 17-year-old girl on Wednesday, February 25, on suspicion of assisting an offender and a man in his 20s the same day on suspicion on murder.