The prisoner released mistakenly from HMP Wandsworth on Monday was let out following a sentence mistake by the court, Paste BN understands.
William 'Billy' Smith had been sentenced to 45 months behind bars for multiple fraud offences at court on Monday, having appeared via a video link from HMP Wandsworth.
However, he was set free after the court mistakenly told the prison that his custodial sentence was instead a suspended one.
A correction was sent from the court to the prison, but it went to the wrong person.
It was not received in time to stop him from leaving.