Linda De Sousa Abreu was arrested by police at Heathrow Airport after footage of her encounter with the detainee went viral on social media.
A prison officer who was filmed having sex with an inmate has pleaded guilty to misconduct in a public office.
Linda De Sousa Abreu, 30, was on duty at HMP Wandsworth prison in London when she entered the prisoner’s cell and had sex with him on June 27.
The meeting was filmed by another inmate and lasted nearly five minutes.
The mother, from Fulham, south-west London, was identified by staff at HMP Wandsworth prison and arrested by the metropolitan police at Heathrow Airport after the video went viral.
She had planned to fly to Madrid and called the prison as she was heading to the airport to say she would not be returning to work.
De Sousa Abreu pleaded guilty to one count of misconduct in a public office at a hearing at Isleworth Crown Court on Monday.
The prosecution alleged that she had wilfully committed misconduct in the exercise of a public function by abusing her position as a prison officer to have sexual relations with a prisoner.
De Sousa Abreu, who holds a Portuguese passport, was granted conditional bail and will appear again at Isleworth Crown Court on November 7.
Tetteh Turkson, of the Crown Prosecution Service, said: “This is a shocking breach of public trust. De Sousa was clearly an enthusiastic participant who wrongly believed she would avoid responsibility.
“The CPS recognises that there is no excuse for any prison officer to behave in this way, and we will never hesitate to prosecute those who abuse their position of power.
“Having worked closely with the Metropolitan Police to build the strongest possible case, De Sousa had no choice but to accept her guilt. She will now have to face the consequences of her actions.”
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De Sousa Abreu’s video emerged just weeks after a watchdog said HMP Wandsworth should be put into emergency lockdown after An inspection raised concerns about continuing deficiencies safe following the The alleged escape of Daniel Khalife in September last year.
The “deeply concerning” inspection also found severe overcrowding, vermin, drugs, violence and an increase in self-harm, with seven prisoners taking their own lives in the past year.
In response, the chief inspector of prisons, Charlie Taylor, wrote to the justice secretary, Alex Chalk, to issue an urgent notice of improvement.
Khalife, 22, is due to stand trial at the Old Bailey in October.
He has pleaded not guilty to the charges against him.
