A judge has praised the efforts of seven Shomrim volunteers who caught gang members who mugged a man at a bus stop in August.
The Shomrim group stopped the gang escaping by car and held the robbers until police arrived.
Judge John Anderson praised their "brave" actions as "an excellent example of public-spirited willingness to take responsibility, at least partially, for the safety of members of the public and they are to be highly commended for what they did".
During the incident in Queens Road, Hendon, the gang took the 24-year-old victim's mobile phone, cash and debit card and threatened to shoot him if he did not reveal his pin number. A Jewish witness called the Shomrim hotline and the volunteers responded within a minute, using three cars to stop the robbers getting away. At the time, police resources were stretched because of the riots in London.
The Shomrim members also gave evidence at the trial of the four gang members.
At Wood Green Crown Court last Thursday, Judge Anderson said: "It is quite clear that the members of the Shomrim on this occasion acted very quickly, properly and effectively and, it must be said, bravely. They made a very significant and impressive contribution to the safety of their community."
Barnet CID's Detective Chief Inspector Mark Hewitt said: "Police and the community owe the Shomrim our thanks for helping to keep Barnet safe."
Shomrim chief executive Gary Ost explained that its work included "ensuring criminals are charged for their behaviour by testifying in court".
Found guilty of robbery, the gang members will be sentenced next month.