Prosecutors are not seeking a re-trial after two men convicted of robbing a student during rioting had their convictions overturned.
John Kafunda and Reece Donovan were jailed in March after a court was told they posed as Good Samaritans before robbing Malaysian Ashraf Rossli, 21, in the summer of last year.
But the two men had their convictions quashed by the Court of Appeal following a private hearing in London.
Appeal judges said they would give their reasons for their decisions at a later date.
The Crown Prosecution Service (CPS) said after the hearing that it would not seek a new trial because there was no realistic prospect of conviction.
A spokeswoman said an issue aired behind closed doors at today's appeal related to the anonymity of two prosecution witnesses.
"Our application for witness anonymity for two witnesses in this trial was allowed by the (trial) judge. Without anonymity being given, these witnesses would not have given evidence," said the CPS spokeswoman.
"The Court of Appeal has quashed these convictions as a result of allowing this application."
She added: "We are not seeking a retrial as the evidence now available without the ability to call these witnesses is not sufficient to provide a realistic prospect of conviction."
Donovan, of Chadwell Heath, east London, was given a five-year jail term after being convicted of offences including robbery and violent disorder.
Kafunda, of Ilford, east London, was given a term of more than four years after being convicted of robbery and violent disorder.
The trial, at Wood Green Crown Court, heard that Mr Rossli had been in Britain for a month when he was knocked to the ground and left a bloodied mess on August 8 2011.
Moments after the attack, he was caught on camera apparently being shepherded from trouble by Good Samaritans.
Footage then showed men rifling through his rucksack as his back was turned.
Clips of the incident were posted on the internet and broadcast on news channels.