Muslim convert Richard Dart has admitted terrorism charges at the Old Bailey.
Dart, Imran Mahmood and Jahangir Alom pleaded guilty on Friday 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 in July 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 and lawyers will have to discuss their basis of plea before the facts are finalised.
An earlier hearing heard that references were made by the men to MI5 and MI5.
Alom, who lived near the Olympics site in Stratford, was arrested in July along with his new bride Ruksana Begum.
In December, she was jailed for a year at the Old Bailey for having al Qaida terrorist material in her mobile phone.
The link between them could not be made until Friday when a court order was lifted.
Begum, 22, who has a first-class accountancy degree, had been married for a month when anti-terrorist officers raided their home.
The court heard that Begum's brothers, Gurukanth Desai and Abdul Miah, pleaded guilty to a plot to blow up the Stock Exchange and were sentenced in February to 12 and 16 years' jail.
Mohammed Chowdhury, who was jailed for 13 years for the same December 2010 plot, asked to marry her but she had never met him.
She married Alom in June, last year, and moved to London with her new husband.
Begum, who lived in Cardiff next door to Miah, pleaded guilty to having material which was likely to be useful to someone committing or preparing an act of terrorism.
This was two editions of al Qaida's Inspire magazine on a micro SD memory card in her mobile.
Begum, of the Provost Estate, Islington, north London, appeared with only her eyes visible beneath a black veil to be sentenced after being remanded in Holloway prison.
Kate Wilkinson, prosecuting, said: "These items contained both instructional and ideological material."
The terrorist material included instructions on remote control detonation, handgun training and how to ignite forest fires."
Hossein Zahir, defending, said Begum downloaded the material a few weeks before because she wanted to understand why her brothers had taken the path they had.
He said: "She was confident that her brothers were innocent and they would be acquitted. Then they pleaded guilty.
"She accessed this material, which is easily accessible, before coming to London to understand the background and ideology which led to her brothers' incarceration.
"She is an intelligent and articulate young woman who does not share the views of others who do not care."