A Scotland Yard detective has been sacked over failures in an investigation involving an associate of Mark Duggan, whose shooting by police sparked nationwide riots in August 2011.
A Metropolitan Police probe into an armed assault by Kevin Hutchinson-Foster, who went on to provide the same gun to Duggan, was found by the police watchdog to have had "a number of failures".
The officer, named only as DC Faulkner, was dismissed without notice after an Independent Police Complaints Commission misconduct hearing which concluded on Friday.
Hutchinson-Foster was jailed in February 2013 for the assault and firearms offences, including supplying the same firearm to Mark Duggan on the day he was fatally shot by a police officer on August 4 2011.
However, the IPCC found that even if the assault had been promptly investigated, it would have been highly unlikely that Hutchinson-Foster could or would have been identified before he provided the gun to Duggan.
The investigation followed a referral from the Metropolitan Police in November 2011 after it identified failings in its original investigation into the assault.
The investigation found a case to answer that CCTV which clearly showed an individual carrying out the assault was not circulated at the earliest opportunity, a number of witnesses were not contacted following the assault and blood swabs were not submitted for forensic analysis for several months.
DC Faulkner was also found to have attempted to deceive his supervisor several months later in an effort to imply that he had circulated the CCTV images shortly after the incident.
In May 2015 a police sergeant was found at a misconduct meeting to have failed to adequately supervise the investigation but no sanction was imposed by the Met.
The IPCC also examined why the Metropolitan Police specialist unit Trident did not immediately act on information the IPCC passed to it on August 12 2011 linking Hutchinson-Foster with the gun found at the scene where Duggan was fatally shot.
A detective chief superintendent (DCS), the then head of Trident, cited perceived confidentiality issues, concerns not to prejudice the IPCC investigation into the shooting of Duggan and a belief that it was the responsibility of others to determine what information could be shared with Hackney borough officers as reasons for the delay.
A detective chief inspector (DCI) from Trident provided similar explanations as well as a need to obtain further supporting evidence to affect an arrest, a focus limited to the supply of the firearm and concerns that any action may spark further public disorder.
IPCC deputy chairwoman Sarah Green said: "A number of explanations were put forward as to why the investigation into an assault did not progress as quickly as it should have.
"Whilst we accept that even if the assault had been promptly investigated, it would have been highly unlikely the assailant could or would have been identified before he provided the gun to Mark Duggan, the investigation was not given the priority it should have been.
"The public needs to feel confident that the police are doing all they can to ensure that these weapons are taken off the streets, including prompt and effective investigations and overcoming perceived difficulties.
"We welcome the fact that Trident has since extended its terms of reference to include a greater emphasis on the unit working with local borough units and other external agencies."
Violence and looting broke out across London and other cities after 29-year-old Mr Duggan was shot in August 2011.
The unrest began in the capital, with shops being looted, buildings set alight and stand-offs with riot police, but it quickly spread to other parts of the country, including Birmingham, Bristol and Manchester over the following few days.