Wandsworth inmate Neil Moore was on remand when he used an illicit mobile phone to create a fake email account.
He posed as a senior court clerk and sent bail instructions to prison staff, who released him on 10 March 2014.
His deception was uncovered when solicitors went to interview him three days later, only to find him gone.
Moore, 28, from Ilford, east London, handed himself in three days later.
Southwark Crown Court heard he had set up a fake web domain which closely resembled that of the court service's official address.
He then emailed the prison's custody inbox with instructions for his release.
The court heard Moore registered the bogus website in the name of investigating officer Det Insp Chris Soole, giving the address and contact details for the Royal Courts of Justice.
Prosecutor Ian Paton said: "A lot of criminal ingenuity harbours in the mind of Mr Moore. The case is one of extraordinary criminal inventiveness, deviousness and creativity, all apparently the developed expertise of this defendant".
The judge, Recorder David Hunt QC, described the behaviour as "ingenious" criminality.
Moore had previously used four different aliases to commit fraud worth Â£1,819,000 in total.
Posing as staff from Barclays Bank, Lloyds Bank, and Santander he managed to persuade large organisations to give him vast sums of money.
Sometimes he answered calls from victims using a man's voice and then pretended to transfer the call to a colleague before resuming the conversation in a woman's voice, the court heard earlier.
He was so convincing police initially co-charged his partner Kristen Moore with the deception. All charges against her have now been dropped.
Moore, who has pleaded guilty to eight counts of fraud and one count of escape from lawful custody, will be sentenced on 20 April.
A convicted fraudster used an "ingenious" escape plot to trick prison wardens into letting him go free, a court has heard.