Ryan Cleary has pleaded guilty to hacking charges in the UK and admitted to being a member of Lulzsec.
Another man, Jake Davis, has also admitted to the charges which include attacking the Serious Organised Crime Agency (SOCA) in the UK.
The two men entered a plea of guilty earlier today while two others, Ryan Ackroyd and a 17-year-old deny the charges.
The trial won't take place until April 2013, however, and doesn't include the offences the men have been charged for in the US.
These include carrying out DDoS attacks against and hacking into computers owned by Fox, Sony, PCS and other companies.
Cleary was recently charged in the US but the courts are yet to decide whether or not he will be extradited to stand trial across the Atlantic.
He made headlines when he was the first suspected Lulzsec member to be arrested in the UK when he was 19. He was bailed on the condition that he stay offline but returned to prison after trying to contact FBI Lulzsec mole Sabu over the web.