Muslim convert Richard Dart admitted terrorism charges at the Old Bailey today.
Dart, Imran Mahmood and Jahangir Alom pleaded guilty to preparing for terrorism or assisting another in terrorism, between July 2010 and July last year.
Dart, 29, of Broadway, Ealing, west London, Mahmood, 21, from Dabbs Hill Lane, Northolt, west London, and Alom, 26, of Abbey Road, Stratford, east London, were arrested between July 5 and 7 last year.
The charges said they travelled to Pakistan for terror training, travelled abroad to commit acts of terrorism and provided information about travel to Pakistan, terrorism training and operational security while there.
They appeared before Mr Justice Simon by prison video-link for a plea and case management hearing. The men had been due to face trial next month.
Dart, the son of teachers from Dorset, appeared in a BBC Three documentary made by his stepbrother after Dart converted to Islam.
In the film, My Brother The Islamist, Dart was said to have been turned into an extremist in months after joining the Muslims Against Crusades group.
Dart, who was said to have changed his name of Salahuddin al-Britani, had reportedly worked as a police community support officer and a BBC security guard.
The three bearded men were remanded in custody for reports before being sentenced on a date to be fixed.
The case against them was that they intended to go to Pakistan to a terrorist camp to be trained for acts of terrorism in the UK and abroad.
Mahmood, who had been to Pakistan before, was able to offer advice and assistance.
Police recovered bits of text messages about their intentions.
One referred to WB, thought to refer to Wootton Bassett through which repatriated British soldiers were driven.
Details of the allegations were not given in court today and lawyers will have to discuss their basis of plea before the facts are finalised.