The alleged al-Qaeda militant was caught crossing through the Olympic Park five times, breaking a ban imposed by the Home Secretary, The Sunday Telegraph has learned.
The 24 year-old has previously tried to get to Afghanistan, allegedly for terrorist training, and is suspected of fighting for the Somali Islamist group al Shabaab, which has been responsible for thousands of deaths, including those of Western aid workers. He is accused of trying to recruit other Britons to its cause.
A Home Office lawyer warned after his discovery in the Olympic area that the man - known as CF - wanted to “re-engage in terrorism-related activities, either in the UK or Somalia” and is “determined to continue to adhere to his Islamist extremist agenda”.
His detention is the most serious security alert yet to hit the Olympic Park.
It is disclosed today after a week which saw 14 terror-related arrests across Britain, including a white Muslim convert detained over an alleged plan to carry out a major terrorist attack.
CF is one of nine suspected risks to national security who are subject to Terrorism Prevention and Investigation Measures (Tpim) - legal orders which restrict their movements and computer use and who they can meet.
They were introduced to replace control orders, which were abolished by the Coalition after long-running controversy over whether they breached human rights and threatened civil liberties.
CF is being prosecuted for breaking the conditions of his order after he was arrested last month and held in police custody. He challenges the banning order at the High Court on Monday.
He is charged with five separate breaches between April and May of an order specifically banning him from using the London Overground rail route which passes through the centre of the Olympic Park.
He apparently travelled from Caledonian Road and Barnsbury station in north London to Stratford, the station for the Games.
Stratford station is beside the Westfield shopping centre which people will go through to get into the Olympic Park, where most of the events are to be held.
The area is heavily protected and regarded by security services and police as among the most significant targets for terrorists.
His presence in the banned zone was discovered because of an electronic tag which he must wear under the conditions of his order, which banned travelling on the route he took or being in the vicinity of the Games.
The tag uses GPS satellite technology to trace his exact movements, and revealed he had passed through the Olympic Park repeatedly.
The latest security scare came to light in a court case involving CF and another terror suspect, known as CC.
Theresa May, the Home Secretary, has compiled a case against CF which says he attempted to travel to Afghanistan to fight jihad and take part in suicide operations in 2008.
He was prosecuted in Britain but absconded during his trial in June 2009 and fled to Somalia. In his absence he was acquitted of any crime.
Officials claim CF, who comes from a large family of Somali origin from north London, attended a terrorist training camp and fought alongside jihadis from the al-Qaeda group al-Shabaab.
The Home Office says CF is linked to a group of six British nationals who received terror training from al-Qaeda leader Saleh Nabhan, who was killed in a dramatic raid by American Navy Seals in 2009, an operation with parallels to the raid last year which killed Osama bin Laden.